Method and apparatus for acquiring a precoding matrix indicator and a precoding matrix

ABSTRACT

In the field of communication technologies, a method and an apparatus for acquiring a Precoding Matrix Indicator (PMI) and a Precoding Matrix (PM) are provided. The method includes: acquiring a reference PMI and a differential PMI according to a first non-differential codebook and a first diagonal differential codebook, where codewords included in the first diagonal differential codebook form a diagonal matrix. The apparatus includes a PMI acquiring module. Acquiring a reference PMI and a differential PMI according to a non-differential codebook and a diagonal differential codebook can reduce the feedback overhead or improve the feedback precision; and the fact that codewords included in the diagonal differential codebook form a diagonal matrix can maintain amplitude characteristics (for example, a constant modulus characteristic, and a finite character set constraint characteristic) of elements of the non-differential codebook or facilitate power distribution among antennas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2011/070323, filed on Jan. 17, 2011, which claims priority toChinese Patent Application No. 201010005350.9, filed on Jan. 16, 2010and Chinese Patent Application No. 201010111526.9, filed on Feb. 11,2010, all of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to the field of communicationtechnologies, and more particularly, to a method and an apparatus foracquiring a Precoding Matrix Indicator (PMI) and a Precoding Matrix(PM).

BACKGROUND OF THE INVENTION

With continuous development of communication technologies, for purposeof improving the performance of data transmission, a data sending end(for example, a node B (NodeB), a base station (BS), or the like) may beconfigured to obtain a PM according to a Precoding Matrix Indicator(PMI) fed back by a data receiving end (for example, a user equipment(UE), a mobile station (MS), or the like) and a codebook pre-storedlocally so that data to be sent are pre-processed through the PM andthen sent to the data receiving end. In this way, a data sending processcan be adaptive to variations in channel statuses so as to improve theperformance of data transmission. Therefore, how to acquire a PMI andwhich kind of codebook is to be used are of vital importance.

The existing Long Term Evolution Release 8 (LTE R8) system supports4-antenna transmission and employs a single fixed codebook which isobtained based on Householder reflection. In the existing Institute ofElectrical and Electronics Engineers (IEEE) 802.16m system, anon-differential codebook and a differential codebook are employed, andfeedback is performed mainly in a differential mode in the followingprocess: in each preset feedback period, the UE firstly feeds back onenon-differential PMI based on the non-differential codebook and then,according to the non-differential PMI, feeds back a plurality ofdifferential PMIs based on the differential codebook in sequence.

During implementation of the present invention, the inventor finds thatat least the following problems exist in the prior art:

In the existing LTE R8 system, a single fixed codebook is employed, thesub-band feedback suffers from a high overhead, and the broadbandfeedback has a low precision. In the existing IEEE 802.16m system, thetime-domain differential feedback is employed, and acquisition of a PMrelies on historical information of the feedback, which may cause theproblem of error propagation. Moreover, because of characteristics ofelements in each of codewords included in the differential codebook usedin the existing IEEE 802.16m system, the PM finally obtained may nothave a constant modulus characteristic, and particularly, it isdifficult to satisfy the finite character set (for example, 8 phaseshift keying (8PSK)) constraint characteristic of each of the elements.Furthermore, it has been found through an experiment that when, in theaforesaid differential feedback, the codebook in the LTE R8 system isdirectly used as the non-differential codebook and the differentialcodebook of the IEEE 802.16m system is employed, the overhead is highand the feedback performance is scarcely improved compared to that whenonly the LTE R8 codebook is used for feedback, resulting in a lowefficiency per feedback bit. Therefore, it is necessary to make furtherresearch on the structure of the feedback and the codebook used for thefeedback in order to improve the feedback performance of the system.

SUMMARY OF THE INVENTION

In order to further improve the feedback performance, embodiments of thepresent invention provide a method and an apparatus for acquiring a PMIand a PM. The technical solutions are as follows.

In one aspect, an embodiment of the present invention provides a methodfor acquiring a PMI, where the method includes:

acquiring a reference PMI and a differential PMI according to a firstnon-differential codebook and a first diagonal differential codebook,where a codeword included in the first diagonal differential codebook isa diagonal matrix.

In one aspect, an embodiment of the present invention provides a methodfor acquiring a PM, where the method includes:

receiving a reference PMI and a differential PMI, where the referencePMI and the differential PMI are obtained according to a firstnon-differential codebook and a first diagonal differential codebook andthen sent by a data receiving end, and a codeword included in the firstdiagonal differential codebook is a diagonal matrix; and

obtaining a PM by using a second non-differential codebook and a seconddiagonal differential codebook pre-stored locally and according to thereference PMI and the differential PMI, where the secondnon-differential codebook and the second diagonal differential codebookare consistent with the first non-differential codebook and the firstdiagonal differential codebook respectively.

In one aspect, an embodiment of the present invention provides anapparatus for acquiring a PMI, where the apparatus includes:

a PMI acquiring module, configured to acquire a reference PMI and adifferential PMI according to a first non-differential codebook and afirst diagonal differential codebook, where a codeword included in thefirst diagonal differential codebook is a diagonal matrix.

In one aspect, an embodiment of the present invention provides anapparatus for acquiring a PM, where the apparatus includes:

a PMI receiving module, configured to receive a reference PMI and adifferential PMI, where the reference PMI and the differential PMI areobtained according to a first non-differential codebook and a firstdiagonal differential codebook and then sent by a data receiving end,and a codeword included in the first diagonal differential codebook is adiagonal matrix; and

a PM acquiring module, configured to, after the reference PMI and thedifferential PMI are received by the PMI receiving module, obtain a PMby using a second non-differential codebook and a second diagonaldifferential codebook pre-stored locally and according to the referencePMI and the differential PMI, where the second non-differential codebookand the second diagonal differential codebook are consistent with thefirst non-differential codebook and the first diagonal differentialcodebook respectively.

In one aspect, an embodiment of the present invention provides a methodfor acquiring a PMI, where the method includes:

calculating a non-differential PMI based on a preset criterion andaccording to a first non-differential codebook, where codewords includedin the first non-differential codebook are obtained from a rotatedHadamard matrix.

In one aspect, an embodiment of the present invention provides a methodfor acquiring a PM, where the method includes:

receiving a non-differential PMI, where the non-differential PMI isobtained according to a first non-differential codebook and then sent bya data receiving end, and codewords included in the firstnon-differential codebook are obtained from a rotated Hadamard matrix;and

obtaining a PM by using a second non-differential codebook pre-storedlocally and according to the non-differential PMI, where the secondnon-differential codebook is consistent with the first non-differentialcodebook.

In one aspect, an embodiment of the present invention provides anapparatus for acquiring a PMI, where the apparatus includes:

a non-differential PMI acquiring module, configured to calculate anon-differential PMI based on a preset criterion and according to afirst non-differential codebook, where codewords included in the firstnon-differential codebook are obtained from a rotated Hadamard matrix.

In one aspect, an embodiment of the present invention provides anapparatus for acquiring a PM, where the apparatus includes:

a non-differential PMI receiving module, configured to receive anon-differential PMI, where the non-differential PMI is obtainedaccording to a first non-differential codebook and then sent by a datareceiving end, and codewords included in the first non-differentialcodebook are obtained from a rotated Hadamard matrix; and

a non-differential PM processing module, configured to, after thenon-differential PMI is received by the PMI receiving module, obtain aPM by using a second non-differential codebook pre-stored locally andaccording to the non-differential PMI, where the second non-differentialcodebook is consistent with the first non-differential codebook.

The technical solutions provided by the embodiments of the presentinvention have the following benefits:

acquiring a reference PMI and a differential PMI according to anon-differential codebook and a diagonal differential codebook canreduce the feedback overhead and improve the feedback precision so as tofurther improve the feedback performance; and the fact that a codewordincluded in the diagonal differential codebook is a diagonal matrix canmaintain amplitude characteristics (for example, a constant moduluscharacteristic, and a finite character set constraint characteristic) ofelements of the non-differential codebook or facilitate powerdistribution among antennas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for acquiring a PMI according toEmbodiment 1 of the present invention;

FIG. 2 is a flowchart of a method for acquiring a PMI according toEmbodiment 2 of the present invention;

FIG. 3 is a flowchart of a method for acquiring a PMI according toEmbodiment 3 of the present invention;

FIG. 4 is a flowchart of a method for acquiring a PMI according toEmbodiment 4 of the present invention;

FIG. 5 is a flowchart of a method for acquiring a PM according toEmbodiment 7 of the present invention;

FIG. 6 is a schematic structure diagram of an apparatus for acquiring aPMI according to Embodiment 8 of the present invention;

FIG. 7 is a schematic structure diagram of an apparatus for acquiring aPM according to Embodiment 9 of the present invention;

FIG. 8 is a flowchart of a method for acquiring a PMI according toEmbodiment 10 of the present invention;

FIG. 9 is a schematic structure diagram of an apparatus for acquiring aPMI according to Embodiment 11 of the present invention;

FIG. 10 is a flowchart of a method for acquiring a PM according toEmbodiment 12 of the present invention; and

FIG. 11 is a schematic structure diagram of an apparatus for acquiring aPM according to Embodiment 13 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, in order to make the objectives, technical solutions andadvantages of the present invention more apparent, the present inventionwill be further described in detail with reference to embodimentsthereof and the accompany drawings.

Embodiment 1

Referring to FIG. 1, this embodiment of the present invention provides amethod for acquiring a PMI, where the method includes the followingsteps.

101: Acquire a reference PMI and a differential PMI according to a firstnon-differential codebook and a first diagonal differential codebook,where a codeword included in the first diagonal differential codebook isa diagonal matrix.

Further, the step of acquiring the reference PMI and the differentialPMI according to the first non-differential codebook and the firstdiagonal differential codebook may include:

calculating the reference PMI based on a preset criterion and accordingto the first non-differential codebook; and

calculating the differential PMI based on the preset criterion andaccording to the first non-differential codebook, the first diagonaldifferential codebook, and the reference PMI; or

the step of acquiring the reference PMI and the differential PMIaccording to the first non-differential codebook and the first diagonaldifferential codebook may include:

calculating the reference PMI and the differential PMI based on thepreset criterion and according to the first non-differential codebookand the first diagonal differential codebook.

Further, a codeword C_(k) included in the first diagonal differentialcodebook has the following structure:C _(k)=diag{e ^(jθ) ^(k,1) ,e ^(jθ) ^(k,2) , . . . ,e ^(jθ) ^(k,i) , . .. ,e ^(jθ) ^(k,N) }

where, k represents a differential PMI included in the first diagonaldifferential codebook D, k=0, 1 . . . |D|−1, |D| represents the numberof codewords included in the first diagonal differential codebook D,j²=−1, N represents the number of transmitting antennas and is apositive integer, θ_(k,i) represents a phase shift, and i=1, 2 . . . N.

Further, the codeword C_(k) included in the first diagonal differentialcodebook has the following structure:C _(k)=diag{e ^(j0·(mθ)) ,e ^(j1*(mθ)) , . . . ,e ^(j(i)*(mθ)) , . . .,e ^(j(N−1)*(mθ))}

where, k represents a differential PMI included in the first diagonaldifferential codebook D, k=0, 1 . . . |D|−1, |D| represents the numberof codewords included in the first diagonal differential codebook D,j²=−1, N represents the number of transmitting antennas and is apositive integer, i*(mθ) represents a phase shift, i=1, 2 . . . N, andmθ represents a phase shift difference between adjacent transmittingantennas.

Further, when, in a dual-polarized transmitting antenna array includingN transmitting antennas, the first N/2 transmitting antennas form agroup of co-polarized transmitting antennas and the remaining N/2transmitting antennas form another group of co-polarized transmittingantennas, the codeword C_(k) included in the first diagonal differentialcodebook has the following structure:C _(k)=diag{S _(m) ,e ^(jθ) ^(n) S _(m)}

where, S_(m)=diag{e^(jθ) ^(m,1) , e^(jθ) ^(m,2) , . . . , e^(jθ) ^(m,i), . . . , e^(jθ) ^(m,N/2) }, k represents a differential PMI included inthe first diagonal differential codebook D, k=0, 1 . . . |D|−1, |D|represents the number of codewords included in the first diagonaldifferential codebook D, j²=−1, N represents the number of transmittingantennas and is an even integer, φ_(n) and θ_(m,i) represent phaseshifts, m and n are natural numbers, and i=1, 2 . . . , N/2.

Further, the codeword C_(k) included in the first diagonal differentialcodebook has the following structure:C _(k)=diag{a _(k,1) e ^(jθ) ^(k,1) ,a _(k,2) e ^(jθ) ^(k,2) , . . . ,a_(k,i) e ^(jθ) ^(k,i) , . . . ,a _(k,N) e ^(jθ) ^(k,N) }

where, k represents a differential PMI included in the first diagonaldifferential codebook D, k=0, 1 . . . |D|−1, |D| represents the numberof codewords included in the first diagonal differential codebook D,j²=−1, N represents the number of transmitting antennas and is apositive integer, a_(k,N) is a real number, θ_(k,i) represents a phaseshift, and i=1, 2 . . . N.

Further, a codeword W_(k) ^((r)) included in the first non-differentialcodebook has the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook W^((r)), i_(k)represents an index of a diagonal matrix R_(i) _(k) corresponding to k,R_(i) _(k) represents a n^(th) order diagonal matrix corresponding toi_(k), j_(k) represents an index of a normalized Hadamard matrixcorresponding to k, H_(n,j) _(k) represents a n^(th) order normalizedHadamard matrix corresponding to j_(k), a value of n is equal to thenumber of the transmitting antennas, and (R_(i) _(k) H_(n,j) _(k))^((r)) represents a matrix formed by selecting r columns from a rotatedHadamard matrix R_(i) _(k) H_(n,j) _(k) .

It should be noted that, R_(i) _(k) H_(n,j) _(k) is obtained throughrotation of column vectors in H_(n,j) _(k) by the diagonal matrix R_(i)_(k) , so it can be called as a rotated Hadamard matrix.

It should be noted that, the structure of the diagonal matrix R_(i) _(k)may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(j δ_(i_(k), 1)), b_(i_(k), 2)𝕖^(j δ_(i_(k), 2)), …  , b_(i_(k), t)𝕖^(jδ_(i_(k), t)), …  , b_(i_(k), n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, j²=−1, t=1, 2, . . . , n, and a value of n is equal to thenumber of the transmitting antennas.

It should be noted that, in the step of forming the matrix (R_(i) _(k)H_(n,j) _(k) )^((r)) by selecting r columns from the rotated Hadamardmatrix R_(i) _(k) H_(n,j) _(k) , which r columns are selected may bedetermined by using a correlation method depending on actualapplications. For example, for uncorrelated channels, the columns shouldbe selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of the antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon.

Further, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of the transmitting antennas,and (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

It should be noted that, R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H) isobtained through rotation of column vectors in H_(n,j) _(k) by thediagonal matrix R_(i) _(k) , so R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H)is also a rotated Hadamard matrix.

It should be noted that, the structure of the diagonal matrix R_(i) _(k)may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(j δ_(i_(k), 1)), b_(i_(k), 2)𝕖^(j δ_(i_(k), 2)), …  , b_(i_(k), t)𝕖^(jδ_(i_(k), t)), …  , b_(i_(k), n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, j²=−1, t=1, 2, . . . , n, and a value of n is equal to thenumber of the transmitting antennas.

It should be noted that, in the step of forming the matrix (R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H), which rcolumns are selected may be determined by using a correlation methoddepending on actual applications. For example, for uncorrelatedchannels, the columns should be selected in such a way that in a set{(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed by extractingone r-column sub-matrix from each matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), each of matrixes has a maximum chordal distance; and forcorrelated channels, columns should be selected in such a way that in aset {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in a zerodirection of a spatial projection of the antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

Further, referring to FIG. 1, after acquiring the reference PMI and thedifferential PMI, the method may further include the following steps.

102: Feed back the reference PMI and the differential PMI to a datasending end; and

103: The data sending end receives the reference PMI and thedifferential PMI and, according to the reference PMI and thedifferential PMI, obtains a PM by using a second non-differentialcodebook and a second diagonal differential codebook pre-stored locally.

The second non-differential codebook and the second diagonaldifferential codebook are consistent with the first non-differentialcodebook and the first diagonal differential codebook respectively.

Further, the first non-differential codebook is a first basic codebook,and the first diagonal differential codebook is a first transformedcodebook.

Further, the second non-differential codebook is a second basiccodebook, and the second diagonal differential codebook is a secondtransformed codebook.

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMI canreduce the feedback overhead and improve the feedback precision so as tofurther improve the feedback performance; and the fact that a codewordincluded in the diagonal differential codebook is a diagonal matrix canmaintain amplitude characteristics (for example, a constant moduluscharacteristic and a finite character set constraint characteristic) ofelements already existing in the non-differential codebook or facilitatepower distribution among antennas. Moreover, a non-differential codebookobtained from a rotated Hadamard matrix may be used. Individual columnsof the Hadamard matrix may be matched with eigenvectors of stronglycorrelated channels and weakly correlated channels in a uniform lineararray transmitting antenna arrangement and a dual-polarized transmittingantenna arrangement respectively so as to improve the accuracy ofquantization. The rotated matrix is in the form of a diagonal matrix,and this can maintain a fine quantization of the space on basis of thequantization of the Hadamard matrix. Furthermore, each of elements ofthe Hadamard matrix is +1 or −1, which can satisfy the constant moduluscharacteristic; and multiplication of the Hadamard matrix with othermatrixes or vectors may be simplified into addition or subtractionoperations, which can significantly reduce the computational complexityof channel quality indicator (CQI) calculation based on a signal tointerference noise ratio (SINR), PMI selection, and rank adaptation. Theindividual columns of the Hadamard matrix are orthogonal to each other,and this can maintain, after normalization, the unitary matrixcharacteristic of codewords in the non-differential codebook so thatindividual transmitted spatial streams are guaranteed to have the samepower distribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Additionally, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.

Embodiment 2

Referring to FIG. 2, this embodiment of the present invention provides amethod for acquiring a PMI, where the method includes the followingsteps.

201: A UE selects to use a differential PMI based on a reference PMI forfeedback, and acquires the reference PMI.

The reference PMI may be a non-differential PMI lately fed back by theUE and, particularly, a non-differential broadband PMI or anon-differential sub-band PMI, which may be selected depending on actualapplications.

In the embodiment of the present invention, the reference PMI is in theform of a non-differential PMI. The reference PMI may at least beobtained in either of the following two ways: 1) calculating thereference PMI as n (may be marked as the reference PMI n) based on apreset criterion and according to a non-differential codebook, as shownin Equation (1):

$\begin{matrix}{n = {\underset{{i = 0},{{1\ldots\;{W^{(r)}}} - 1},{W_{i} \in W^{(r)}}}{\arg\mspace{11mu}\max}\;{f( W_{i} )}}} & (1)\end{matrix}$

where, |W^((r))| represents the size of the non-differential codebookW^((r)), that is, the number of codewords included in thenon-differential codebook W^((r)); r represents a rank of the codewordsincluded in the non-differential codebook W^((r)); W_(i) represents acodeword in the non-differential codebook W^((r)) corresponding to areference PMI i; and f(W_(i)) represents an objective functioncorresponding to the preset criterion.

It should be noted that, the aforesaid preset criterion may be athroughput maximization criterion, and the objective functioncorresponding to this criterion may be a throughput maximizationfunction, which may be achieved based on information capacitycalculation or based on mutual information or variants of mutualinformation (for example, weighting of mutual information). Furthermore,the aforesaid preset criterion may also be a chordal-distancemaximization criterion. Of course, the objective function correspondingto the preset criterion may further be set flexibly depending on actualapplications, and no limitation is made thereon. The preset criterion(s)described elsewhere is similar to that described here, so no furtherdescription will be made thereon.

Specifically, the non-differential codebook W^((r)) may be anon-differential codebook set according to the embodiment of the presentinvention. The codewords in the non-differential codebook W^((r)) areobtained from a rotated Hadamard matrix, and specifically, a codewordW_(k) ^((r)) included in the non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in thenon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the non-differentialcodebook W^((r)), r represents a rank of the codewords included in thenon-differential codebook, i_(k) represents an index of a diagonalmatrix R_(i) _(k) corresponding to k, R_(i) _(k) represents a n^(th)order diagonal matrix corresponding to i_(k), j_(k) represents an indexof a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) )^((r)) represents a matrix formed by selectingr columns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) .

It should be noted that, the structure of the diagonal matrix R_(i) _(k)may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(j δ_(i_(k), 1)), b_(i_(k), 2)𝕖^(j δ_(i_(k), 2)), …  , b_(i_(k), t)𝕖^(jδ_(i_(k), t)), …  , b_(i_(k), n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, j²=−1, t=1, 2, . . . , n, and a value of n is equal to thenumber of transmitting antennas.

It should be noted that, in the step of forming the matrix (R_(i) _(k)H_(n,j) _(k) )^((r)) by selecting r columns from the rotated Hadamardmatrix R_(i) _(k) H_(n,j) _(k) , which r columns are selected may bedetermined by using a correlation method depending on actualapplications. For example, for uncorrelated channels, the columns shouldbe selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of an antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon. Forexample, for a 4-bit 8-antenna non-differential codebook, the codewordis

${W_{k}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{k}}H_{8,j_{k}}} )^{(r)}}},$where: i_(k)=0, 1, 2, 3, j_(k)=0, 1, 2, 3, it is supposed thatk=j_(k)*4+i_(k) (it should be noted that, the present invention is notlimited to this form, and any other feasible form may be adopteddepending on actual applications; for example, it may also be supposedthat k=i_(k)*4+j_(k)), and r=1, 2 . . . 8. For example, when r=1, W_(k)⁽¹⁾=(R_(i) _(k) H_(8,j) _(k) )⁽¹⁾, where (R_(i) _(k) H_(8,j) _(k) )⁽¹⁾represents an operation of taking one of the columns (for example, thefirst column) of R_(i) _(k) H_(8,j) _(k) . Cases where r=2, 3 . . . 8are similar to the case where r=1, so no further description will bemade thereon. H_(8,0), H_(8,1), H_(8,2) and H_(8,3) are as follows:

${H_{8.0} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\1 & 1 & 1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} & {- 1} & 1 & {- 1} & 1 \\1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 \\1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 \\1 & {- 1} & {- 1} & 1 & {- 1} & 1 & 1 & {- 1}\end{bmatrix}}},{H_{8.1} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 & 1 & 1 & {- 1} & {- 1} \\{- 1} & 1 & 1 & {- 1} & 1 & {- 1} & {- 1} & 1 \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\{- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 & 1 & 1 \\{- 1} & 1 & {- 1} & 1 & 1 & {- 1} & 1 & {- 1}\end{bmatrix}}}$ ${H_{8.2} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & 1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} & {- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 & 1 & 1 & 1 & {- 1} & {- 1} \\{- 1} & 1 & 1 & {- 1} & 1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1}\end{bmatrix}}},{H_{8.3} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 \\1 & {- 1} & {- 1} & 1 & {- 1} & 1 & 1 & {- 1} \\{- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} \\{- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 & 1 & 1 \\{- 1} & 1 & {- 1} & 1 & 1 & {- 1} & 1 & {- 1} \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1}\end{bmatrix}}}$

Diagonal elements of R_(i) _(k) may be selected to be consistent with8-point Discrete Fourier Transformation (DFT) vectors, which are asfollows:

${R_{0} = {{diag}\{ {1,1,1,1,1,1,1,1} \}}},{R_{1} = {{diag}\{ {1,j,{- 1},{- j},1,j,{- 1},{- j}} \}}},{R_{2} = {{diag}\{ {1,{\mathbb{e}}^{j\frac{\pi}{4}},{\mathbb{e}}^{j\frac{2\pi}{4}},{\mathbb{e}}^{j\frac{3\pi}{4}},{- 1},{- {\mathbb{e}}^{j\frac{\pi}{4}}},{- {\mathbb{e}}^{j\frac{2\pi}{4}}},{- {\mathbb{e}}^{j\frac{3\pi}{4}}}} \}}},{and}$$R_{3} = {{diag}{\{ {1,{\mathbb{e}}^{{- j}\frac{\pi}{4}},{\mathbb{e}}^{{- j}\frac{2\pi}{4}},{\mathbb{e}}^{{- j}\frac{3\pi}{4}},{- 1},{- {\mathbb{e}}^{{- j}\frac{\pi}{4}}},{- {\mathbb{e}}^{{- j}\frac{2\pi}{4}}},{- {\mathbb{e}}^{{- j}\frac{3\pi}{4}}}} \}.}}$

Additionally, a full-rank precoding codebook may be given as shown inTable 1 or Table 2 below.

TABLE 1 Normalized Hadamard matrix Diagonal rotation matrix R_(i)H_(8.0) H_(8.1) H_(8.2) H_(8.3) diag{1, 1, 1, 1, 1, 1, 1, 1) W₀ ⁽⁸⁾ W₂⁽⁸⁾ W₈ ⁽⁸⁾ W₁₀ ⁽⁸⁾${diag}\{ {1,\; e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$W₄ ⁽⁸⁾ W₆ ⁽⁸⁾${diag}\{ {1,\; e^{j\frac{\pi}{2}},e^{j\frac{2\pi}{2}},e^{j\frac{3\pi}{2}},e^{j\frac{4\pi}{2}},e^{j\frac{5\pi}{2}},e^{j\frac{6\pi}{2}},e^{j\frac{7\pi}{2}}} \}$W₁ ⁽⁸⁾ W₃ ⁽⁸⁾ W₉ ⁽⁸⁾ W₁₁ ⁽⁸⁾${diag}\{ {1,\; e^{j\frac{3\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{9\pi}{4}},e^{j\frac{12\pi}{4}},e^{j\frac{15\pi}{4}},e^{j\frac{18\pi}{4}},e^{j\frac{21\pi}{4}}} \}$W₅ ⁽⁸⁾ W₇ ⁽⁸⁾ diag{1, 1, 1, -1, 1, 1, 1, -1} W₁₂ ⁽⁸⁾ W₁₄ ⁽⁸⁾ W₁₃ ⁽⁸⁾ W₁₅⁽⁸⁾

or

TABLE 2 Diagonal rotation matrix Normalized Hadamard matrix R_(i)H_(8,0) H_(8,1) H_(8,2) H_(8,3) diag {1, 1, 1, 1, 1, 1, 1, 1} W₀ ⁽⁸⁾ W₂⁽⁸⁾ W₈ ⁽⁸⁾ W₁₀ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$W₄ ⁽⁸⁾ W₆ ⁽⁸⁾ W₁₂ ⁽⁸⁾ W₁₄ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{2}},e^{j\frac{2\pi}{2}},e^{j\frac{3\pi}{2}},e^{j\frac{4\pi}{2}},e^{j\frac{5\pi}{2}},e^{j\frac{6\pi}{2}},e^{j\frac{7\pi}{2}}} \}$W₁ ⁽⁸⁾ W₃ ⁽⁸⁾ W₉ ⁽⁸⁾ W₁₁ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{9\pi}{4}},e^{j\frac{12\pi}{4}},e^{j\frac{15\pi}{4}},e^{j\frac{18\pi}{4}},e^{j\frac{21\pi}{4}}} \}$W₅ ⁽⁸⁾ W₇ ⁽⁸⁾ W₁₃ ⁽⁸⁾ W₁₅ ⁽⁸⁾

Under the condition that a nested characteristic is met, other low-rankprecoding codebooks can be derived from the aforesaid full-rankprecoding codebook.

Specifically, the codeword W_(k) ^((r)) included in the non-differentialcodebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the non-differential codebookW^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents the number ofcodewords included in the non-differential codebook W^((r)), rrepresents a rank of the codewords included in the non-differentialcodebook W^((r)), i_(k) represents an index of a diagonal matrix R_(i)_(k) corresponding to k, R_(i) _(k) represents a n^(th) order diagonalmatrix corresponding to i_(k), j_(k) represents an index of a normalizedHadamard matrix corresponding to k, H_(n,j) _(k) represents a n^(th)order normalized Hadamard matrix corresponding to j_(k), a value of n isequal to the number of transmitting antennas, and (R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H))^((r)) represents a matrix formed by selecting rcolumns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H).

It should be noted that, the structure of the diagonal matrix R_(i) _(k)may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(j δ_(i_(k), 1)), b_(i_(k), 2)𝕖^(j δ_(i_(k), 2)), …  , b_(i_(k), t)𝕖^(jδ_(i_(k), t)), …  , b_(i_(k), n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, j²=−1, t=1, 2, . . . , n, and a value of n is equal to thenumber of transmitting antennas.

It should be noted that, in the step of forming the matrix (R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H), which rcolumns are selected may be determined by using a correlation methoddepending on actual applications. For example, for uncorrelatedchannels, the columns should be selected in such a way that in a set{(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed by extractingone r-column sub-matrix from each matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), each of matrixes has a maximum chordal distance; and forcorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in a zerodirection of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

For example, for a 4-bit 8-antenna non-differential codebook, thecodeword is

${W_{k}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{k}}H_{8,j_{k}}R_{i_{k}}^{H}} )^{(r)}}},$where: i_(k)=0, 1, 2, 3, j_(k)=0, 1, 2, 3, it is supposed thatk=j_(k)*4+i_(k) (it should be noted that, the present invention is notlimited to this form, and any other feasible form may be adopteddepending on actual applications; for example, it may also be supposedthat k=i_(k)*4+j_(k)), and r=1, 2 . . . 8. When r=1, W_(k) ⁽¹⁾=(R_(i)_(k) H_(8,j) _(k) R_(i) _(k) ^(H))⁽¹⁾, where (R_(i) _(k) H_(8,j) _(k)R_(i) _(k) ^(H))⁽¹⁾ represents an operation of taking one of the columns(for example, the first column) of R_(i) _(k) H_(8,j) _(k) R_(i) _(k)^(H). Cases where r=2, 3 . . . 8 are similar to the case where r=1, sono further description will be made thereon. H_(8,0), H_(8,1), H_(8,2)and H_(8,3) are as follows:

${H_{8.0} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\1 & 1 & 1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} & {- 1} & 1 & {- 1} & 1 \\1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 \\1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 \\1 & {- 1} & {- 1} & 1 & {- 1} & 1 & 1 & {- 1}\end{bmatrix}}},{H_{8.1} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 & 1 & 1 & {- 1} & {- 1} \\{- 1} & 1 & 1 & {- 1} & 1 & {- 1} & {- 1} & 1 \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\{- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 & 1 & 1 \\{- 1} & 1 & {- 1} & 1 & 1 & {- 1} & 1 & {- 1}\end{bmatrix}}}$ ${H_{8.2} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & 1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} & {- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 & 1 & 1 & 1 & {- 1} & {- 1} \\{- 1} & 1 & 1 & {- 1} & 1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1}\end{bmatrix}}},{H_{8.3} = {\frac{1}{\sqrt{8}}\begin{bmatrix}1 & 1 & {- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 \\1 & {- 1} & {- 1} & 1 & {- 1} & 1 & 1 & {- 1} \\{- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & 1 & {- 1} & {- 1} & 1 & 1 & {- 1} \\{- 1} & {- 1} & {- 1} & {- 1} & 1 & 1 & 1 & 1 \\{- 1} & 1 & {- 1} & 1 & 1 & {- 1} & 1 & {- 1} \\1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} & 1 & {- 1} & 1 & {- 1}\end{bmatrix}}}$

Diagonal elements of R_(i) _(k) may be selected to be consistent withthe 8-point DFT vectors, which are as follows:

${R_{0} = {{diag}\{ {1,1,1,1,1,1,1,1} \}}},{R_{1} = {{diag}\{ {1,j,{- 1},{- j},1,j,{- 1},{- j}} \}}},{R_{2} = {{diag}\{ {1,{\mathbb{e}}^{j\frac{\pi}{4}},{\mathbb{e}}^{j\frac{2\pi}{4}},{\mathbb{e}}^{j\frac{3\pi}{4}},{- 1},{- {\mathbb{e}}^{j\frac{\pi}{4}}},{- {\mathbb{e}}^{j\frac{2\pi}{4}}},{- {\mathbb{e}}^{j\frac{3\pi}{4}}}} \}}},{R_{3} = {{diag}{\{ {1,{\mathbb{e}}^{{- j}\frac{\pi}{4}},{\mathbb{e}}^{{- j}\frac{2\pi}{4}},{\mathbb{e}}^{{- j}\frac{3\pi}{4}},{- 1},{- {\mathbb{e}}^{{- j}\frac{\pi}{4}}},{- {\mathbb{e}}^{{- j}\frac{2\pi}{4}}},{- {\mathbb{e}}^{{- j}\frac{3\pi}{4}}}} \}.}}}$

Additionally, a full-rank precoding codebook may be given as shown inTable 3 or Table 4.

TABLE 3 Diagonal rotation matrix Normalized Hadamard matrix R_(i)H_(8,0) H_(8,1) H_(8,2) H_(8,3) diag {1, 1, 1, 1, 1, 1, 1, 1} W₀ ⁽⁸⁾ W₂⁽⁸⁾ W₈ ⁽⁸⁾ W₁₀ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$W₄ ⁽⁸⁾ W₆ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{2}},e^{j\frac{2\pi}{2}},e^{j\frac{3\pi}{2}},e^{j\frac{4\pi}{2}},e^{j\frac{5\pi}{2}},e^{j\frac{6\pi}{2}},e^{j\frac{7\pi}{2}}} \}$W₁ ⁽⁸⁾ W₃ ⁽⁸⁾ W₉ ⁽⁸⁾ W₁₁ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{9\pi}{4}},e^{j\frac{12\pi}{4}},e^{j\frac{15\pi}{4}},e^{j\frac{18\pi}{4}},e^{j\frac{21\pi}{4}}} \}$W₅ ⁽⁸⁾ W₇ ⁽⁸⁾ diag {1, 1, 1, −1, 1, 1, 1, −1} W₁₂ ⁽⁸⁾ W₁₄ ⁽⁸⁾ W₁₃ ⁽⁸⁾W₁₅ ⁽⁸⁾ or

or

TABLE 4 Diagonal rotation matrix Normalized Hadamard matrix R_(i)H_(8,0) H_(8,1) H_(8,2) H_(8,3) diag {1, 1, 1, 1, 1, 1, 1, 1} W₀ ⁽⁸⁾ W₂⁽⁸⁾ W₈ ⁽⁸⁾ W₁₀ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$W₄ ⁽⁸⁾ W₆ ⁽⁸⁾ W₁₂ ⁽⁸⁾ W₁₄ ⁽⁸⁾${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{2}},e^{j\frac{2\pi}{2}},e^{j\frac{3\pi}{2}},e^{j\frac{4\pi}{2}},e^{j\frac{5\pi}{2}},e^{j\frac{6\pi}{2}},e^{j\frac{7\pi}{2}}} \}$W₁ ⁽⁸⁾ W₃ ⁽⁸⁾ W₉ ⁽⁸⁾ W₁₁ ⁽⁸⁾${diag}\{ {1,{\mathbb{e}}^{j\frac{3\pi}{4}},{\mathbb{e}}^{j\frac{6\pi}{4}},{\mathbb{e}}^{j\frac{9\pi}{4}},{\mathbb{e}}^{j\frac{12\pi}{4}},{\mathbb{e}}^{j\frac{15\pi}{4}},{\mathbb{e}}^{j\frac{18\pi}{4}},{\mathbb{e}}^{j\frac{21\pi}{4}}} \}$W₅ ⁽⁸⁾ W₇ ⁽⁸⁾ W₁₃ ⁽⁸⁾ W₁₅ ⁽⁸⁾

Under the condition that a nesting characteristic is met, other low-rankprecoding codebooks can be derived from the aforesaid full-rankprecoding codebook.

Specifically, the codeword W_(k) ^((r)) included in the non-differentialcodebook may have the following structure:W _(k) ^((r)) =R _(i) _(k) B _(n,j) _(k) ^((r))

where, k represents a PMI included in the non-differential codebookW^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents the number ofcodewords included in the non-differential codebook W^((r)), rrepresents a rank of the codewords included in the non-differentialcodebook W^((r)), i_(k) represents an index of a diagonal matrix R_(i)_(k) corresponding to k, R_(i) _(k) represents a n^(th) order diagonalmatrix corresponding to i_(k), B_(n,j) _(k) ^((r)) represents a codewordin a non-differential codebook having a rank of r for n transmittingantennas and corresponding to an index j_(k), and j_(k) corresponds tok.

It should be noted that, the structure of the diagonal matrix R_(i) _(k)may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i_(k), 2)𝕖^(jδ_(i_(k), 2)), …  , b_(i_(k), t)𝕖^(jδ_(i_(k), t)), …  , b_(i_(k), n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, j²=−1, t=1, 2, . . . , n, and a value of n is equal to thenumber of transmitting antennas.

Moreover, the non-differential codebook may also be any non-differentialcodebook known in the prior art (for example, an LTE R8 codebook) andmay be flexibly selected depending on actual applications, and nolimitation is made thereon herein.

2) selecting a non-differential broadband PMI (supposing that thenon-differential broadband PMI is n) lately fed back by the UE for useas the reference PMI.

Specifically, the NodeB may, through a high-level signaling or adownlink physical control channel, instruct the UE to use thedifferential PMI based on the reference PMI for feedback, and afterreceiving the instruction from the NodeB, the UE selects to use thedifferential PMI based on the reference PMI for feedback. Alternatively,the NodeB and the UE make beforehand an agreement that the UE uses thedifferential PMI based on the reference PMI for feedback so that whenperforming the feedback, the UE automatically selects to use thedifferential PMI based on the reference PMI for feedback. The presentinvention is not merely limited to the aforesaid two approaches, and anyother feasible approach may be set depending on actual applications sothat the UE can select to use the differential PMI based on thereference PMI for feedback.

202: The UE feeds back the reference PMI to the NodeB, and calculatesthe differential PMI based on the preset criterion and according to thereference PMI, the non-differential codebook W^((r)), and the diagonaldifferential codebook D.

The non-differential codebook W^((r)) may be a non-differential codebooksimilar to that in the step 201 (that is, the codewords set in theembodiment of the present invention obtained from a non-differentialcodebook obtained from a rotated Hadamard matrix), or may be anynon-differential codebook known in the prior art.

The diagonal differential codebook is a differential codebook whosecodewords are diagonal matrixes according to the embodiment of thepresent invention. The structure of a codeword C_(k) included in thediagonal differential codebook D according to the embodiment of thepresent invention is as shown in Equation (2):C _(k)=diag{e ^(jθ) ^(k,1) ,e ^(jθ) ^(k,2) , . . . ,e ^(jθ) ^(k,i) , . .. ,e ^(jθ) ^(k,N) }  (2)

where, k represents a differential PMI included in the diagonaldifferential codebook D, k=0, 1 . . . |D|−1, |D| represents the numberof codewords included in the differential codebook D, j²=−1, Nrepresents the number of transmitting antennas and is a positiveinteger, θ_(k,i)(i=1, 2, 3 . . . N) represents a phase shift, andθ_(k,i) may be obtained according to the number of the transmittingantennas and arrangement of the transmitting antennas.

The differential PMI is calculated as k (marked as the differential PMIk) based on the preset criterion and according to the reference PMI, thenon-differential codebook W^((r)) and the diagonal differential codebookD, as shown in Equation (3):

$\begin{matrix}{\mspace{79mu}{k = {\underset{{i = 0},{{1\ldots{D}} - 1},{C_{i} \in D}}{\arg\;\max}\mspace{14mu}{f( {C_{i}W_{n}} )}}}} & (3)\end{matrix}$

where, C_(i) represents a codeword in the diagonal differential codebookD corresponding to a differential PMI i, W_(n) represents a codeword inthe non-differential codebook W^((r)) corresponding to a reference PMIn, and f(C_(i)W_(n)) represents an objective function corresponding tothe preset criterion.

203: The UE feeds back the differential PMI to the NodeB.

In the embodiment of the present invention, the differential PMI is k,so k is fed back to the NodeB.

204: The NodeB receives the reference PMI and the differential PMI, andcalculates a PM {circumflex over (V)} by using the non-differentialcodebook W^((r)) and the diagonal differential codebook D and accordingto the reference PMI and the differential PMI.

It should be noted that, because the UE already feeds back the referencePMI to the NodeB in the step 202 before feeding back the differentialPMI to the NodeB in the step 203, the NodeB firstly receives thereference PMI and then receives the differential PMI. Therefore, theNodeB may store the reference PMI that is firstly received and then,after the differential PMI is received, calculate the PM {circumflexover (V)} according to the reference PMI and the differential PMI.

Specifically, for a Single User Multiple Input Multiple Output (SU-MIMO)system, the NodeB obtains a codeword corresponding to the reference PMIthrough query from the non-differential codebook W^((r)) (consistentwith a non-differential codebook pre-stored in the UE) pre-stored in theNodeB according to the reference PMI, obtains a codeword correspondingto the differential PMI through query from the diagonal differentialcodebook D (consistent with a diagonal differential codebook pre-storedin the UE) pre-stored in the NodeB according to the differential PMI,and multiplies the codeword corresponding to the reference PMI by thecodeword corresponding to the differential PMI to obtain amultiplication result for use as the PM {circumflex over (V)}.

In the embodiment of the present invention, the reference PMI is n, acodeword corresponding to the reference PMI n is W_(n), the differentialPMI is k, and a codeword corresponding to the differential PMI k isC_(k). Therefore, the PM {circumflex over (V)} obtained according to theembodiment of the present invention is as shown in Equation (4):{circumflex over (V)}=C _(k) W _(n)  (4)

For a Multiple User Multiple Input Multiple Output (MU-MIMO) system, theNodeB calculates, by using the non-differential codebook W^((r)) and thediagonal differential codebook D, the PM {circumflex over (V)} based ona Zero-Forcing Beam Forming (ZF-BF) algorithm or a maximumSignal-Leakage Plus Noise Ratio (SLNR) criterion and according toreference PMIs and differential PMIs fed back by individual UEs that aresimultaneously paired.

The process for the individual UEs to feed back the PMIs is similar tothe steps 201-203, and will not be further described herein. Moreover,for ease of understanding of the calculation process in case of theMU-MIMO system, a case where the PM {circumflex over (V)} is calculatedby using the ZF-BF algorithm will be described as an examplehereinafter:

For two UEs that are simultaneously paired, suppose that a reference PMIcorresponding to one of the two UEs is n₁ (and suppose that a codewordcorresponding to the reference PMI n₁ is W_(n1)), and that adifferential PMI corresponding to the one of the two UEs is k₁ (andsuppose that a codeword corresponding to the differential PMI k₁ isC_(k1)); and suppose that a reference PMI corresponding to the other UEis n₂ (and suppose that a codeword corresponding to the reference PMI n₂is W_(n2)), and that a differential PMI corresponding to the other UE isk₂ (and suppose that a codeword corresponding to the differential PMI k₂is C_(k2)). Then, by using the aforesaid method for the SU-MIMO system,a PM {circumflex over (V)}₁ corresponding to the one of the two UEs iscalculated as shown in Equation (5) and a PM {circumflex over (V)}₂corresponding to the other UE is calculated as shown in Equation (6):{circumflex over (V)} ₁ =C _(k1) W _(n1)  (5){circumflex over (V)} ₂ =C _(k2) W _(n2)  (6)

Ĥ=[({circumflex over (V)}₁)^(T) ({circumflex over (V)}₂)^(T)]^(T) andG=Ĥ^(H)(ĤĤ^(H))⁻¹ are set.

A PM {circumflex over (V)} obtained according to Ĥ and G is as shown inEquation (7):

$\begin{matrix}{\hat{V} = {\frac{P}{\sqrt{S}}G\;{diag}\{ {{g_{0}}^{- 1},{{g_{1}}^{- 1}\mspace{14mu}\ldots\mspace{14mu}{g_{i}}^{- 1}\mspace{14mu}\ldots\mspace{14mu}{g_{S - 1}}^{- 1}}}\; \}}} & (7)\end{matrix}$

where, P represents a total transmitting power of the NodeB, Srepresents the total number of layers for spatial multiplexing of thetwo UEs, g_(i)(i=0, 1 . . . S−1) represents an i^(th) column vector ofG, and ∥g_(i)∥(i=0, 1 . . . S−1) represents an Euclid norm of G.

The process for calculating the PM {circumflex over (V)} based on themaximum SLNR criterion is similar to that in the prior art, and will notbe further described herein.

205: The NodeB pre-processes data s to be sent by using the PM{circumflex over (V)}, and sends the pre-processed data s to the UEthrough the transmitting antennas.

206: The UE receives a receive signal y, and detects data of the receivesignal y.

Specifically, the receive signal y received by the UE is as shown inEquation (8):y=H{circumflex over (V)}s+n  (8)

where, y represents a receive signal received by the UE, H represents achannel matrix, {circumflex over (V)} represents a PM, s represents datato be sent, and n represents Additive White Gaussian Noise (AWGN).

It should be noted that, in the aforesaid process, the reference PMI andthe differential PMI are fed back to the NodeB in the step 202 and thestep 203 respectively; however, in actual applications, the referencePMI and the differential PMI may also be fed back to the NodeBsimultaneously. Specifically, after obtaining the reference PMI, the UEmay firstly store the reference PMI; and then, in the step 203, the UEfeeds back the reference PMI and the differential PMI to the NodeBsimultaneously. Alternatively, it is possible to, in the step 201,calculate the reference PMI as n and the differential PMI as ksimultaneously based on the preset criterion and according to thenon-differential codebook W^((r)) and the diagonal differential codebookD, as shown in Equation (9):

$\begin{matrix}{\mspace{79mu}{( {k,n} ) = {\underset{\underset{{j = 0},1,\ldots\mspace{14mu},{{W^{(r)}} - 1},{W_{j} \in W^{(r)}}}{{i = 0},1,\ldots\mspace{14mu},{{D} - 1},{C_{i} \in D}}}{\arg\;\max}{f( {C_{i}W_{j}} )}}}} & (9)\end{matrix}$

Then, after the reference PMI and the differential PMI are fed back tothe NodeB simultaneously in the step 202, the step 204 is executeddirectly.

Moreover, it should be noted that, in the aforesaid process of feedingback the reference PMI and the differential PMI, whether thedifferential PMI or the reference PMI is fed back, it is possible thatone PMI is fed back for the whole system bandwidth; or, provided thatthe system is divided into a plurality of bandwidth parts (BPs) and eachof the BPs includes a plurality of sub-bands, then it is possible thatone PMI is fed back for each of the sub-bands or for multiple ones ofthe sub-bands (for example, the Best-M manner: one PMI is fed back forthe selected M sub-band(s)). That is, the reference PMI and thedifferential PMI may be either a broadband PMI or a sub-band PMI, andalso one PMI may be fed back for a plurality of sub-bands in the Best-Mmanner.

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can satisfy the constant moduluscharacteristic; and multiplication of the Hadamard matrix with othermatrixes or vectors may be simplified into addition or subtractionoperations, which can significantly reduce the computational complexityof CQI calculation based on the SINR, PMI selection and rank adaptation.The individual columns of the Hadamard matrix are orthogonal to eachother, and this can maintain, after normalization, the unitary matrixcharacteristic of codewords in the non-differential codebook so thatindividual sent spatial streams are guaranteed to have the same powerdistribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Further, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.Additionally, using the non-differential PMI that is lately fed back bythe UE as the reference PMI can not only reduce the overhead but alsomake full use of the correlation of channels in the frequency domain andthe time domain or in the space domain, thereby improving feedbackprecision.

Embodiment 3

Referring to FIG. 3, this embodiment of the present invention provides amethod for acquiring a PMI, where the method includes the followingsteps.

301: A UE selects to use a differential PMI based on a reference PMI forfeedback, and acquires the reference PMI.

The reference PMI may be a non-differential PMI and a differential PMIthat are lately fed back by the UE.

In the embodiment of the present invention, the reference PMI mayinclude a non-differential PMI and m reference differential PMIs (m is anatural number, and a value of m may be determined depending on actualapplications, for example, depending on the number of sub-bands). Byusing the approach described in the step 201 of Embodiment 2, thenon-differential PMI may be obtained as n. Furthermore, m referencedifferential PMIs may be calculated as n₀, n₁, . . . , n_(m) based on apreset criterion and according to a diagonal differential codebook D(the m reference differential PMIs are marked as the referencedifferential PMI n₀, the reference differential PMI n₁, . . . , and thereference differential PMI n_(m) respectively), as shown in Equation(10):

$\begin{matrix}{( {n_{0},{n_{1}\mspace{14mu}\ldots\mspace{14mu} n_{m}}} ) = {\underset{{({i_{0},i_{1},\ldots\mspace{14mu},i_{m}})},{i_{j} = 0},{{1\ldots\mspace{14mu}{D}} - 1},{C_{i_{j}} \in D},{j = 0},1,\ldots\mspace{14mu},m}{\arg\;\max}{f( \mspace{11mu}{C_{i_{m}}\;\ldots\mspace{14mu} C_{i_{1}}C_{i_{0}}W_{n}} )}}} & (10)\end{matrix}$

302: The UE feeds back the reference PMI to the NodeB, and calculatesthe differential PMI based on the preset criterion and according to thereference PMI, a non-differential codebook W^((r)), and the diagonaldifferential codebook D.

The non-differential codebook W^((r)) and the diagonal differentialcodebook D are identical to those in the step 202 of Embodiment 2respectively, and will not be further described herein.

The differential PMI is calculated as k (marked as the differential PMIk) based on the preset criterion and according to the reference PMI (n,n₀, n₁, . . . , n_(m)), the non-differential codebook W^((r)), and thediagonal differential codebook D, as shown in Equation (11):

$\begin{matrix}{\mspace{79mu}{k = {\underset{{i = 0},{{1\mspace{14mu}\ldots\mspace{14mu}{D}} - 1},{C_{i} \in D}}{argmax}{f( {C_{i}( {C_{n_{m}}\mspace{14mu}\ldots\mspace{14mu} C_{n_{1}}C_{n_{0}}W_{n}} )} )}}}} & (11)\end{matrix}$

where, C_(i) represents a codeword in the diagonal differential codebookD corresponding to a differential PMI i; C_(n) ₀ C_(n) ₁ . . . C_(n)_(m) represent codewords in the diagonal differential codebook Dcorresponding to the reference differential PMI n₀, the referencedifferential PMI n₁, . . . , and the reference differential PMI n_(m)respectively; and W_(n) represents a codeword in the non-differentialcodebook W^((r)) corresponding to the non-differential PMI n.

303: The UE feeds back the differential PMI to the NodeB.

In the embodiment of the present invention, the differential PMI is k,so k is fed back to the NodeB.

304: The NodeB receives the reference PMI and the differential PMI, andcalculates a PM {circumflex over (V)} by using the non-differentialcodebook W^((r)) and the diagonal differential codebook D and accordingto the reference PMI and the differential PMI.

Specifically, for an SU-MIMO system, the NodeB obtains a codewordcorresponding to the reference PMI through query from thenon-differential codebook W^((r)) (consistent with a non-differentialcodebook pre-stored in the UE) pre-stored in the NodeB according to thereference PMI, obtains a codeword corresponding to the differential PMIthrough query from the diagonal differential codebook D (consistent witha diagonal differential codebook pre-stored in the UE) pre-stored in theNodeB according to the differential PMI, and multiplies the codewordcorresponding to the reference PMI by the codeword corresponding to thedifferential PMI to obtain a multiplication result for use as the PM{circumflex over (V)}.

In the embodiment of the present invention, the reference PMI includes anon-differential PMI and m reference differential PMIs, thenon-differential PMI is n, the m reference differential PMIs are n₀, n₁,. . . , n_(m) respectively, a codeword corresponding to thenon-differential PMI n is W_(n), codewords corresponding to thereference differential PMIs n₀, n₁, . . . , n_(m) are C_(n) ₀ , C_(n) ₁. . . C_(n) _(m) respectively, the differential PMI is k, and a codewordcorresponding to the differential PMI k is C_(k). Therefore, the PM{circumflex over (V)} obtained according to the embodiment of thepresent invention is as shown in Equation (12):{circumflex over (V)}=C _(k)(C _(n) _(m) . . . C _(n) ₁ C _(n) ₀ W_(n))  (12)

For an MU-MIMO system, the NodeB calculates, by using thenon-differential codebook W^((r)) and the diagonal differential codebookD, the PM {circumflex over (V)} based on the ZF-BF algorithm or themaximum SLNR criterion and according to reference PMIs and differentialPMIs fed back by individual UEs that are simultaneously paired. Thisprocess is similar to the step 204 of Embodiment 2, and will not befurther described herein.

305: The NodeB pre-processes data s to be sent by using the PM{circumflex over (V)}, and sends the pre-processed data s to the UEthrough the transmitting antennas.

306: The UE receives a receive signal y, and detects data of the receivesignal y.

Specifically, the receive signal Y received by the UE is as shown inEquation (13):y=H{circumflex over (V)}s+n  (13)

where, y represents a receive signal received by the UE, H represents achannel matrix, {circumflex over (V)} represents a PM, s represents datato be sent, and n represents AWGN.

It should be noted that, in the aforesaid process, the reference PMI andthe differential PMI are fed back to the NodeB in the step 302 and thestep 303 respectively; however, in actual applications, the referencePMI and the differential PMI may also be fed back to the NodeBsimultaneously. Specifically, after obtaining the reference PMI, the UEmay firstly store the reference PMI; and then, in the step 303, the UEfeeds back the reference PMI and the differential PMI to the NodeBsimultaneously. Alternatively, it is possible to, in the step 301,calculate the reference PMI as n, n₀, n₁, . . . , n_(m) and thedifferential PMI as k simultaneously based on the preset criterion andaccording to the non-differential codebook W^((r)) and the diagonaldifferential codebook D, as shown in Equation (14a):

$\begin{matrix}{( {k,n,n_{0},{n_{1}\mspace{14mu}\ldots\mspace{14mu} n_{m}}} ) = {\underset{{{W^{(r)}} - 1},{{W_{l} \in W^{(r)}};{i_{j} = 0}},{{1\ldots\mspace{14mu}{D}} - 1},{C_{i_{j}} \in D},{j = 0},1,\ldots\mspace{14mu},{m.}}{\underset{{({i,l,i_{0},i_{1},\ldots\mspace{14mu},i_{m}})},{i = 0},{{1\ldots\mspace{14mu}{D}} - 1},{{C_{i} \in D};{l = 0}},1,\ldots\mspace{14mu},}{\arg\;\max}}{f( {C_{i}C_{i_{m}}\;\ldots\mspace{14mu} C_{i_{1}}C_{i_{0}}W_{l}} )}}} & ( {14\; a} )\end{matrix}$

Moreover, it should be noted that, the reference differential PMIs inthe step 301 may also be achieved recursively, as shown in Equation(14b):

$\begin{matrix}{{n_{j} = {\underset{{i_{j} = 0},{{1\ldots\mspace{14mu}{D}} - 1},{C_{i_{j}} \in D}}{\arg\;\max}{f( {C_{i_{j}}( {C_{i_{j - 1}}\mspace{14mu}\ldots\mspace{14mu} C_{i_{1}}C_{i_{0}}W_{n}} )} )}}},{j = 0},1,\ldots\mspace{14mu},m} & ( {14\; b} )\end{matrix}$

Then, after the reference PMI and the differential PMI are fed back tothe NodeB simultaneously in the step 302, the step 304 is executeddirectly.

Moreover, it should be noted that, in the aforesaid process of feedingback the reference PMI and the differential PMI, whether thedifferential PMI or the reference PMI is fed back, it is possible thatone PMI is fed back for the whole system bandwidth; or, provided thatthe system is divided into a plurality of BPs and each of the BPsincludes a plurality of sub-bands, one PMI is fed back for each of thesub-bands or for multiple ones of the sub-bands (for example, the Best-Mmanner: one PMI is fed back for the M selected sub-band(s)). That is,the reference PMI and the differential PMI may be either a broadband PMIor a sub-band PMI, and also one PMI may be fed back for a plurality ofsub-bands in the Best-M manner.

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can maintain the constant moduluscharacteristic of the non-differential codebook; and multiplication ofthe Hadamard matrix with other matrixes or vectors may be simplifiedinto addition or subtraction operations, which can significantly reducethe computational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation. The individual columns of the Hadamardmatrix are orthogonal to each other, and this can maintain the unitarymatrix characteristic of codewords in the non-differential codebook sothat individual sent spatial streams are guaranteed to have the samepower distribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Further, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.Additionally, using the non-differential PMI and the m referencedifferential PMIs that are lately fed back by the UE as the referencePMI can not only further reduce the overhead but also make full use ofthe correlation of channels in the frequency domain and the time domainor in the space domain, further improving feedback precision.

The methods described in Embodiment 2 and Embodiment 3 are alsoapplicable to a Coordinated Multiple Point transmission (CoMP) system.Hereinafter, a case where the methods are applied to the CoMP systemwill be further described as an example.

Embodiment 4

Referring to FIG. 4, this embodiment of the present invention provides amethod for acquiring a PMI, where the method includes the followingsteps.

401: A UE selects to use a differential PMI based on a reference PMI forfeedback, and acquires the reference PMI of each cell.

Specifically, BSs in all cells of the CoMP system where the UE islocated can, through a high-level signaling or a downlink physicalcontrol channel, instruct the UE to use the differential PMI based onthe reference PMI for feedback, and after receiving the instruction, theUE selects to use the differential PMI based on the reference PMI forfeedback. Moreover, it should be noted that, in the embodiment of thepresent invention, the BSs in all the cells of the CoMP system arecentrally controlled by an evolved NodeB (eNode B).

In the embodiment of the present invention, it is supposed that the CoMPsystem has M cells in total (M is a positive integer), and the referencePMI of each of the cells is n₁, n₂, . . . , n_(M) respectively. Itshould be noted that, in the embodiment of the present invention, thereference PMI of each of the cells may be in the form of either thereference PMI described in the step 201 of Embodiment 2 or the referencePMI described in the step 301 of Embodiment 3, and may be selectedflexibly depending on actual applications.

402: The UE feeds back the reference PMI of each of the cells to theeNode B, and calculates the differential PMI of each of the cells basedon a preset criterion and according to the reference PMI of each of thecells, a non-differential codebook W^((r)), and a diagonal differentialcodebook D.

The non-differential codebook W^((r)) is identical to that in the step202 of Embodiment 2, and will not be further described herein. Thediagonal differential codebook D may be identical to that in the step202 of Embodiment 2, or may be a diagonal matrix obtained bymultiplication of each of matrixes in the diagonal differential codebookin the step 202 of Embodiment 2 with one phase shift matrix (forexample, multiplication of C_(k) with diag{e^(jζ) ^(k) , e^(jζ) ^(k) , .. . , e^(jζ) ^(k) , . . . , e^(jζ) ^(k) }).

The differential PMI of each of the cells is calculated as k₁, k₂ . . .k_(M) respectively based on the preset criterion and according to thereference PMI of each of the cells, the non-differential codebookW^((r)) and the diagonal differential codebook D, as shown in Equation(15):

$\begin{matrix}{( {k_{1}k_{2}\mspace{14mu}\ldots\mspace{14mu} k_{M}} ) = {\underset{{({i_{1}i_{2}\mspace{14mu}\ldots\mspace{14mu} i_{M}})},{C_{ij} \in D},{j = 1},\ldots\mspace{14mu},M}{\arg\;\max}{f( {{norm} \quad\{ \lbrack {( {\sqrt{p_{1}}C_{i_{1}}W_{n_{1}}} )^{H}( {\sqrt{p_{2}}C_{i_{2}}W_{n_{2}}} )^{H}\mspace{14mu}\ldots\mspace{14mu}( {\sqrt{p_{M}}C_{i_{M}}W_{n_{M}}} )^{H}} \rbrack \}^{H} )} }}} & (15)\end{matrix}$

where, M represents the number of cells and is a positive integer; C_(i)₁ , C_(i2) . . . C_(iM) represent codewords in the diagonal differentialcodebook D corresponding to the differential PMIs i₁, i₂, . . . , i_(M)respectively; W_(n) ₁ , W_(n) ₂ . . . W_(n) _(M) represent codewords inthe non-differential codebook W^((r)) corresponding to the referencePMIs n₁, n₂, . . . , n_(M) respectively; f(•) represents an objectivefunction corresponding to the preset criterion; p_(i) representslong-scale fading corresponding from the UE to a BS of a cell i and is apower control parameter known by both the eNode B and the UE; norm{•}represents normalization of individual columns of a matrix; i₁=0, 1 . .. |D|−1, C_(i) ₁ εD, i₂=0, 1 . . . |D|−1, C_(i) ₂ εD, . . . i_(M)=0, 1 .. . |D|−1, C_(i) _(M) εD; and (•)^(H) represents a conjugate transposeoperation of a matrix or vectors.

403: The UE feeds back the differential PMI of each of the cells to theeNode B.

In the embodiment of the present invention, the differential PMIs of allthe cells are k₁, k₂ . . . k_(M) respectively, so k₁, k₂ . . . k_(M) arefed back to the eNode B.

404: The eNode B receives the reference PMI and the differential PMI ofeach of the cells, and calculates a PM {circumflex over (V)} of each ofthe cells by using the non-differential codebook W^((r)) and thediagonal differential codebook D and according to the reference PMI andthe differential PMI.

In the embodiment of the present invention, there are M cells in total,and it is supposed that the PM {circumflex over (V)} of each of thecells is the PM {circumflex over (V)}₁, the PM {circumflex over (V)}₂, .. . , and the PM {circumflex over (V)}_(M) respectively. The eNode Bcalculates the PM {circumflex over (V)} of each of the cells by usingthe non-differential codebook W^((r)) and the diagonal differentialcodebook D and according to the reference PMI and the differential PMI,as shown in Equation (16):(({circumflex over (V)}₁)^(H)({circumflex over (V)}₂)^(H) . . .({circumflex over (V)}_(M))^(H))^(H)=norm{[(√{square root over (p ₁)}C_(i) ₁ W _(n) ₁ )^(H)(√{square root over (p ₂)}C _(i) ₂ W _(n) ₂ )^(H) .. . (√{square root over (p _(M))}C _(i) _(M) W _(n) _(M))^(H)]}^(H)  (16)

where, M represents the number of cells and is a positive integer; C_(i)₁ , C_(i2) . . . C_(iM) represent codewords in the diagonal differentialcodebook D corresponding to the differential PMIs i₁, i₂, . . . , i_(M)respectively; W_(n) ₁ , W_(n) ₂ . . . W_(n) _(M) represent codewords inthe non-differential codebook W^((r)) corresponding to the referencePMIs n₁, n₂, . . . , n_(M) respectively; p_(i) represents long-scalefading corresponding from the UE to a BS of a cell i and is a powercontrol parameter known by both the eNode B and the UE; norm{•}represents normalization of individual columns of a matrix; (•)^(H)represents a conjugate transpose operation of a matrix or vectors; andi₁=0, 1 . . . |D|−1, C_(i) ₁ εD, i₂=0, 1 . . . |D|−1, C_(i) ₂ εD . . .i_(M)=0, 1 . . . |D|−1, C_(i) _(M) εD.

405: The eNode B pre-processes data s to be sent of each of the cells byusing the PM {circumflex over (V)} of the cell, and sends thepre-processed data s to the UE through the transmitting antennas.

406: The UE receives a receive signal y, and detects data of the receivesignal y.

Specifically, the receive signal y received by the UE is as shown inEquation (17):y=diag{H ₁ ,H ₂ , . . . ,H _(i) , . . . ,H _(M)}norm{[(√{square rootover (p ₁)}C _(i) ₁ W _(n) ₁ )^(H)(√{square root over (p ₂)}C _(i) ₂ W_(n) ₂ )^(H) . . . (√{square root over (p _(M))}C _(i) _(M) W _(n) _(M))^(H)]}^(H) s+n  (17)

where, H_(i)(i=1, 2 . . . M) represents a channel matrix from the UE toa BS of a cell i; and other symbols therein have the same meanings asthose in Equation (15) and Equation (16), and will not be furtherdescribed herein.

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can maintain the constant moduluscharacteristic of the non-differential codebook; and multiplication ofthe Hadamard matrix with other matrixes or vectors may be simplifiedinto addition or subtraction operations, which can significantly reducethe computational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation. The individual columns of the Hadamardmatrix are orthogonal to each other, and this can maintain the unitarymatrix characteristic of codewords in the non-differential codebook sothat individual sent spatial streams are guaranteed to have the samepower distribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Further, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.Additionally, the method can acquire the reference PMI and thedifferential PMI of each of the cells and can be applied to the CoMPsystem, which enlarges the application scope thereof.

Additionally, it should be noted that, in consideration of powerdistribution of the transmitting antennas, the structure of the codewordC_(k) included in the diagonal differential codebook in Embodiments 2-4may also be as shown in Equation (18):C _(k)=diag{a _(k,1) e ^(jθ) ^(k,1) ,a _(k,2) e ^(jθ) ^(k,2) , . . . ,a_(k,i) e ^(jθ) ^(k,i) , . . . ,a _(k,N) e ^(jθ) ^(k,N) }  (18)

where, k represents the differential PMI in the diagonal differentialcodebook D, k=0, 1 . . . |D|−1, |D| represents the number of codewordsincluded in the diagonal differential codebook D, j²=−1, N representsthe number of transmitting antennas and is a positive integer, a_(k,i)is a real number, θ_(k,i)(i=1, 2, 3 . . . N) represents a phase shift ofan i^(th) transmitting antenna, and θ_(k,i) may be obtained according tothe number of the transmitting antennas and the arrangement of thetransmitting antennas. A value of a_(k,i)e^(jθ) ^(k,i) (i=1, 2 . . . N)may be set depending on actual applications, for example, may beobtained through selection from constellation points of a constellationdiagram of 16 Quadrature Amplitude Modulation (16QAM), 64QAM or thelike. When the codewords in the diagonal differential codebook have astructure as shown in Equation (18), the power distribution of thetransmitting antennas can be implemented.

Embodiment 5

It should be noted that, this embodiment of the present inventiondiffers from Embodiments 1-4 in that, for a strongly-correlatedtransmitting antenna arrangement, the structure of the codeword C_(k)included in the diagonal differential codebook in Embodiments 1-4 mayfurther be optimized as shown in Equation (19):C _(k)=diag{e ^(j0·(mθ)) ,e ^(j1*(mθ)) , . . . ,e ^(j)(i)*(mθ), . . . ,e^(j(N−1)*(mθ))}  (19)

where, k represents a differential PMI included in the diagonaldifferential codebook D, k=0, 1 . . . |D|−1, |D| represents the numberof codewords included in the diagonal differential codebook D, j²=−1, Nrepresents the number of transmitting antennas and is a positiveinteger, i*(mθ) represents a phase shift of an i^(th) transmittingantenna, i=1, 2 . . . N, and mθ represents a phase shift differencebetween adjacent transmitting antennas.

Furthermore, it should be noted that, the aforesaid diagonal elementsmay also have their positions swapped according to the specific antennaarrangement, for example, having their positions shifted circularlyalong the diagonal or all the diagonal elements being multiplied by onephase shift factor.

It should be noted that, values of the phase shift difference mθ shouldbe distributed symmetrically around 0 as much as possible; and as longas the feedback overhead allows, more differential matrixes may bedistributed around the 0 phase shift; for example, a value of m may be:m=0, ±1, ±2, ±4, ±8, ±16, ±32, ±64 . . . . For example, in theembodiment of the present invention, a 2-bit 4-antenna diagonaldifferential codebook is as shown in Table 5 and Table 8, a 3-bit4-antenna diagonal differential codebook is as shown in Table 6 andTable 9, and a 4-bit 4-antenna diagonal differential codebook is asshown in Table 7 and Table 10; also, a 2-bit 8-antenna diagonaldifferential codebook is as shown in Table 11 and Table 14, a 3-bit8-antenna diagonal differential codebook is as shown in Table 12 andTable 15, and a 4-bit 8-antenna diagonal differential codebook is asshown in Table 13 and Table 16.

TABLE 5 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {1,e^{j\frac{- \pi}{16}},e^{j\frac{{- 2}\pi}{16}},e^{j\frac{{- 3}\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}}} \}$

TABLE 6 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}}} \}$2${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{4\pi}{8}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}}} \}$4${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{4}},e^{{- j}\frac{2\pi}{4}},e^{{- j}\frac{3\pi}{4}}} \}$5 diag {1, j, −1, −j} 6 diag {1, −j, −1, j} 7 diag {1, −1, 1, −1}

TABLE 7 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}}} \}$4${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}}} \}$5${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{9\pi}{16}}} \}$6${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{9\pi}{16}}} \}$7${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}}} \}$8${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}}} \}$9${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{9\pi}{8}}} \}$10${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{9\pi}{8}}} \}$11 diag {1, j, −1, −j} 12 diag {1, −j, −1, j} 13${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{4}},{- j},e^{j\frac{\pi}{4}}} \}$14${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{4}},j,e^{{- j}\frac{\pi}{4}}} \}$15 diag {1, −1, 1, −1}

TABLE 8 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {e^{j\frac{- \pi}{16}},e^{j\frac{{- 2}\pi}{16}},e^{j\frac{{- 3}\pi}{16}},e^{j\frac{{- 4}\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}}} \}$

TABLE 9 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\{ {{\mathbb{e}}^{j\frac{\pi}{8}},{\mathbb{e}}^{j\frac{2\pi}{8}},{\mathbb{e}}^{j\frac{3\pi}{8}},{\mathbb{e}}^{j\frac{4\pi}{8}}} \}$2${diag}\{ {{\mathbb{e}}^{{- j}\frac{\pi}{8}},{\mathbb{e}}^{{- j}\frac{2\pi}{8}},{\mathbb{e}}^{{- j}\frac{3\pi}{8}},{\mathbb{e}}^{{- j}\frac{4\pi}{8}}} \}$3${diag}\{ {{\mathbb{e}}^{j\frac{\pi}{4}},{\mathbb{e}}^{j\frac{2\pi}{4}},{\mathbb{e}}^{j\frac{3\pi}{4}},{\mathbb{e}}^{j\frac{4\pi}{4}}} \}$4${diag}\{ {{\mathbb{e}}^{{- j}\frac{\pi}{4}},{\mathbb{e}}^{{- j}\frac{2\pi}{4}},{\mathbb{e}}^{{- j}\frac{3\pi}{4}},{\mathbb{e}}^{{- j}\frac{4\pi}{4}}} \}$5 diag {j, −1, −j, 1} 6 diag {−j, −1, j, 1} 7 diag {−1, 1, −1, 1}

TABLE 10 Differential PMI Differential PM 0 diag {1, 1, 1, 1} 1${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{4\pi}{16}}} \}$3${diag}\{ {{\mathbb{e}}^{j\frac{\pi}{8}},{\mathbb{e}}^{j\frac{2\pi}{8}},{\mathbb{e}}^{j\frac{3\pi}{8}},{\mathbb{e}}^{j\frac{4\pi}{8}}} \}$4${diag}\{ {{\mathbb{e}}^{{- j}\frac{\pi}{8}},{\mathbb{e}}^{{- j}\frac{2\pi}{8}},{\mathbb{e}}^{{- j}\frac{3\pi}{8}},{\mathbb{e}}^{{- j}\frac{4\pi}{8}}} \}$5${diag}\{ {{\mathbb{e}}^{j\frac{3\pi}{16}},{\mathbb{e}}^{j\frac{6\pi}{16}},{\mathbb{e}}^{j\frac{9\pi}{16}},{\mathbb{e}}^{j\frac{12\pi}{16}}} \}$6${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{9\pi}{16}},e^{{- j}\frac{12\pi}{16}}} \}$7${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}}} \}$8${diag}\{ {{\mathbb{e}}^{{- j}\frac{\pi}{4}},{\mathbb{e}}^{{- j}\frac{2\pi}{4}},{\mathbb{e}}^{{- j}\frac{3\pi}{4}},{\mathbb{e}}^{{- j}\frac{4\pi}{4}}} \}$9${diag}\mspace{11mu}\{ {e^{j\frac{3\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{9\pi}{8}},e^{j\frac{12\pi}{8}}} \}$10${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{9\pi}{8}},e^{{- j}\frac{12\pi}{8}}} \}$11${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{2}},e^{j\frac{2\pi}{2}},e^{j\frac{3\pi}{2}},e^{j\frac{4\pi}{2}}} \}$12${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{2}},e^{{- j}\frac{2\pi}{2}},e^{{- j}\frac{3\pi}{2}},e^{{- j}\frac{4\pi}{2}}} \}$13${diag}\mspace{11mu}\{ {e^{j\frac{3\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{9\pi}{4}},e^{j\frac{12\pi}{4}}} \}$14${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{4}},e^{{- j}\frac{6\pi}{4}},e^{{- j}\frac{9\pi}{4}},e^{{- j}\frac{12\pi}{4}}} \}$15 diag {e^(jπ), e^(j2π), e^(j3π), e^(j4π)}

TABLE 11 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}},e^{j\frac{5\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{7\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{4\pi}{16}},e^{{- j}\frac{5\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{7\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}}} \}$

TABLE 12 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}}} \}$2${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{4\pi}{8}},e^{{- j}\frac{5\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{7\pi}{8}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$4${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{4}},e^{{- j}\frac{2\pi}{4}},e^{{- j}\frac{3\pi}{4}},e^{{- j}\frac{4\pi}{4}},e^{{- j}\frac{5\pi}{4}},e^{{- j}\frac{6\pi}{4}},e^{{- j}\frac{7\pi}{4}}} \}$5 diag {1, j, −1, −j, 1, j, −1, −j} 6 diag {1,−j, −1, j, 1, −j, −1, j} 7diag {1, −1, 1, −1, 1, −1, 1, −1}

TABLE 13 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}},e^{j\frac{5\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{7\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{4\pi}{16}},e^{{- j}\frac{5\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{7\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}}} \}$4${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{4\pi}{8}},e^{{- j}\frac{5\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{7\pi}{8}}} \}$5${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{9\pi}{16}},e^{j\frac{12\pi}{16}},e^{j\frac{15\pi}{16}},e^{j\frac{18\pi}{16}},e^{j\frac{21\pi}{16}}} \}$6${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{9\pi}{16}},e^{{- j}\frac{12\pi}{16}},e^{{- j}\frac{15\pi}{16}},e^{{- j}\frac{18\pi}{16}},e^{{- j}\frac{21\pi}{16}}} \}$7${diag}\mspace{11mu}\{ {1,e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}}} \}$8${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{\pi}{4}},e^{{- j}\frac{2\pi}{4}},e^{{- j}\frac{3\pi}{4}},e^{{- j}\frac{4\pi}{4}},e^{{- j}\frac{5\pi}{4}},e^{{- j}\frac{6\pi}{4}},e^{{- j}\frac{7\pi}{4}}} \}$9${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{9\pi}{8}},e^{j\frac{12\pi}{8}},e^{j\frac{15\pi}{8}},e^{j\frac{18\pi}{8}},e^{j\frac{21\pi}{8}}} \}$10${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{9\pi}{8}},e^{{- j}\frac{12\pi}{8}},e^{{- j}\frac{15\pi}{8}},e^{{- j}\frac{18\pi}{8}},e^{{- j}\frac{21\pi}{8}}} \}$11 diag {1, j, −1, −j, 1, j, −1, −j} 12 diag {1, −j, −1, j, 1, −j, −1,j} 13${diag}\mspace{11mu}\{ {1,e^{j\frac{3\pi}{4}},{- j},e^{j\frac{\pi}{4}},{- 1},{- e^{j\frac{3\pi}{4}}},j,{- e^{j\frac{\pi}{4}}}} \}$14${diag}\mspace{11mu}\{ {1,e^{{- j}\frac{3\pi}{4}},j,e^{{- j}\frac{\pi}{4}},{- 1},{- e^{{- j}\frac{3\pi}{4}}},{- j},{- e^{{- j}\frac{\pi}{4}}}} \}$15 diag {1, −1, 1, −1, 1, −1, 1, −1}

TABLE 14 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}},e^{j\frac{5\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{7\pi}{16}},e^{j\frac{8\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{4\pi}{16}},e^{{- j}\frac{5\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{7\pi}{16}},e^{{- j}\frac{8\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}},e^{j\frac{8\pi}{8}}} \}$

TABLE 15 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}},e^{j\frac{8\pi}{8}}} \}$2${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{4\pi}{8}},e^{{- j}\frac{5\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{7\pi}{8}},e^{{- j}\frac{8\pi}{8}}} \}$3${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{4}},e^{j\frac{2\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{4\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{6\pi}{4}},e^{j\frac{7\pi}{4}},e^{j\frac{8\pi}{4}}} \}$4${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{4}},e^{{- j}\frac{2\pi}{4}},e^{{- j}\frac{3\pi}{4}},e^{{- j}\frac{4\pi}{4}},e^{{- j}\frac{5\pi}{4}},e^{{- j}\frac{6\pi}{4}},e^{{- j}\frac{7\pi}{4}},e^{{- j}\frac{8\pi}{4}}} \}$5 diag {j, −1, −j, 1, j, −1, −j, 1} 6 diag {−j, −1, j, 1, −j, −1, j, 1}7 diag {−1, 1, −1, 1, −1, 1, −1, 1}

TABLE 16 Differential PMI Differential PM 0 diag {1, 1, 1, 1, 1, 1, 1,1} 1${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{16}},e^{j\frac{2\pi}{16}},e^{j\frac{3\pi}{16}},e^{j\frac{4\pi}{16}},e^{j\frac{5\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{7\pi}{16}},e^{j\frac{8\pi}{16}}} \}$2${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{16}},e^{{- j}\frac{2\pi}{16}},e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{4\pi}{16}},e^{{- j}\frac{5\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{7\pi}{16}},e^{{- j}\frac{8\pi}{16}}} \}$3${diag}\mspace{11mu}\{ {e^{j\frac{\pi}{8}},e^{j\frac{2\pi}{8}},e^{j\frac{3\pi}{8}},e^{j\frac{4\pi}{8}},e^{j\frac{5\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{7\pi}{8}},e^{j\frac{8\pi}{8}}} \}$4${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{8}},e^{{- j}\frac{2\pi}{8}},e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{4\pi}{8}},e^{{- j}\frac{5\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{7\pi}{8}},e^{{- j}\frac{8\pi}{8}}} \}$5${diag}\mspace{11mu}\{ {e^{j\frac{3\pi}{16}},e^{j\frac{6\pi}{16}},e^{j\frac{9\pi}{16}},e^{j\frac{12\pi}{16}},e^{j\frac{15\pi}{16}},e^{j\frac{18\pi}{16}},e^{j\frac{21\pi}{16}},e^{j\frac{24\pi}{16}}} \}$6${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{16}},e^{{- j}\frac{6\pi}{16}},e^{{- j}\frac{9\pi}{16}},e^{{- j}\frac{12\pi}{16}},e^{{- j}\frac{15\pi}{16}},e^{{- j}\frac{18\pi}{16}},e^{{- j}\frac{21\pi}{16}},e^{{- j}\frac{24\pi}{16}}} \}$8${diag}\mspace{11mu}\{ {e^{{- j}\frac{\pi}{4}},e^{{- j}\frac{2\pi}{4}},e^{{- j}\frac{3\pi}{4}},e^{{- j}\frac{4\pi}{4}},e^{{- j}\frac{5\pi}{4}},e^{{- j}\frac{6\pi}{4}},e^{{- j}\frac{7\pi}{4}},e^{{- j}\frac{8\pi}{4}}} \}$9${diag}\mspace{11mu}\{ {e^{j\frac{3\pi}{8}},e^{j\frac{6\pi}{8}},e^{j\frac{9\pi}{8}},e^{j\frac{12\pi}{8}},e^{j\frac{15\pi}{8}},e^{j\frac{18\pi}{8}},e^{j\frac{21\pi}{8}},e^{j\frac{24\pi}{8}}} \}$10${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{8}},e^{{- j}\frac{6\pi}{8}},e^{{- j}\frac{9\pi}{8}},e^{{- j}\frac{12\pi}{8}},e^{{- j}\frac{15\pi}{8}},e^{{- j}\frac{18\pi}{8}},e^{{- j}\frac{21\pi}{8}},e^{{- j}\frac{24\pi}{8}}} \}$11 diag {j, −1, −j, 1, j, −1, −j, 1} 12 diag {−j, −1, j, 1, −j, −1, j,1} 13${diag}\mspace{11mu}\{ {e^{j\frac{3\pi}{4}},{- j},e^{j\frac{\pi}{4}},{- 1},{- e^{j\frac{3\pi}{4}}},j,{- e^{j\frac{\pi}{4}}},1} \}$14${diag}\mspace{11mu}\{ {e^{{- j}\frac{3\pi}{4}},j,e^{{- j}\frac{\pi}{4}},{- 1},{- e^{{- j}\frac{3\pi}{4}}},{- j},{- e^{{- j}\frac{\pi}{4}}},1} \}$15 diag {−1, 1, −1, 1, −1, 1, −1, 1}

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can satisfy the constant moduluscharacteristic; and multiplication of the Hadamard matrix with othermatrixes or vectors may be simplified into addition or subtractionoperations, which can significantly reduce the computational complexityof CQI calculation based on the SINR, PMI selection and rank adaptation.The individual columns of the normalized Hadamard matrix are orthogonalto each other, and this can maintain the unitary matrix characteristicof codewords in the non-differential codebook so that individual sentspatial streams are guaranteed to have the same power distribution and,in case of a full rank, individual transmitting antennas have the samepower distribution. Furthermore, the approach to obtain anon-differential codebook from a rotated Hadamard matrix may be appliedto cases where the number of transmitting antennas is 2, 4, 8, 16, 32,64 or the like, and the obtained non-differential codebook may satisfythe constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.Additionally, the feedback performance can be further improved throughfurther optimization of the codewords in the diagonal differentialcodebook.

Embodiment 6

With increase of transmitting antennas, a dual-polarized transmittingantenna array will become a universal arrangement. Therefore, thisembodiment of the present invention provides a method for acquiring aPMI. This method differs from the methods described in Embodiments 2-5in that, the method according to the embodiment of the present inventionacquires a diagonal differential codebook of a dual-polarizedtransmitting antenna array (which may be referred to as a dual-polarizeddiagonal differential codebook) by using a diagonal differentialcodebook of monopolar transmitting antennas (which may be referred to asa monopolar diagonal differential codebook) in Embodiment 2-5.

Specifically, when, in a dual-polarized transmitting antenna arrayincluding N transmitting antennas, the first N/2 (1^(st), 2^(nd),3^(rd), . . . , N/2^(th)) transmitting antennas form a group ofco-polarized transmitting antennas and the remaining N/2 (N/2+1^(th),N/2+2^(th), . . . , N^(th)) transmitting antennas form another group ofco-polarized transmitting antennas, the codeword C_(k) included in thediagonal differential codebook has a structure as shown in Equation(20):C _(k)=diag{S _(m) ,e ^(jφ) ^(n) S _(m)}  (20)

where, S_(m)=diag{e^(jθ) ^(m,1) , e^(jθ) ^(m,2) , . . . , e^(jθ) ^(m,i), . . . , e^(jθ) ^(m,N/2) }, k represents a differential PMI included inthe diagonal differential codebook D, k=0, 1 . . . |D|−1, |D| representsthe number of codewords included in the diagonal differential codebookD, j²=−1, N represents the number of transmitting antennas and is aneven integer, φ_(n) and θ_(m,i) represent phase shift parameters, m andn are natural numbers, and i=1, 2 . . . , N/2.

It should be noted that, in the matrix of Equation (20), the first N/2diagonal elements correspond to a group of co-polarized transmittingantennas and the remaining N/2 diagonal elements correspond to anothergroup of co-polarized transmitting antennas. Moreover, if thearrangement of the dual-polarized transmitting antenna array changes,then it just needs to have positions of the aforesaid elements swappedcorrespondingly; and the structure is similar to those described before,and will not be further described herein.

In the method for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can satisfy the constant moduluscharacteristic; and multiplication of the Hadamard matrix with othermatrixes or vectors may be simplified into addition or subtractionoperations, which can significantly reduce the computational complexityof CQI calculation based on the SINR, PMI selection and rank adaptation.The individual columns of the normalized Hadamard matrix are orthogonalto each other, and this can maintain the unitary matrix characteristicof codewords in the non-differential codebook so that individual sentspatial streams are guaranteed to have the same power distribution and,in case of a full rank, individual transmitting antennas have the samepower distribution. Furthermore, the approach to obtain anon-differential codebook from a rotated Hadamard matrix may be appliedto cases where the number of transmitting antennas is 2, 4, 8, 16, 32,64 or the like, and the obtained non-differential codebook may satisfythe constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.Additionally, forming a diagonal differential codebook of adual-polarized transmitting antenna array by using a diagonaldifferential codebook of monopolar transmitting antennas can make fulluse of features of the dual-polarized transmitting antenna array so asto improve the performance of the diagonal differential codebook in thedual-polarized transmitting antenna array arrangement.

The methods in Embodiments 2-6 have been described by taking thedownlink system (where the NodeB sends data to the UE) as an example. Itshould be noted that, the methods described in Embodiments 2-6 are alsoapplicable to an uplink system (for example, a system where the UE sendsdata to the NodeB). The methods described in Embodiments 2-6 applied tothe uplink system differs from those applied to the downlink system inthat: the NodeB acquires a reference PMI and a differential PMI andnotifies the UE of the reference PMI and the differential PMI in stepssimilar to those of Embodiments 2-6; and the UE receives thenotification from the NodeB and performs precoding, and sends data tothe NodeB, which receives and detects the data.

Embodiment 7

Referring to FIG. 5, this embodiment of the present invention provides amethod for acquiring a PM, where the method includes the followingsteps.

501: Receive a reference PMI and a differential PMI.

The reference PMI and the differential PMI are obtained according to afirst non-differential codebook and a first diagonal differentialcodebook and then sent by a data receiving end, and a codeword includedin the first diagonal differential codebook is a diagonal matrix.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention.Codewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order normalized Hadamard matrixcorresponding to j_(k), a value of n is equal to the number oftransmitting antennas, and (R_(i) _(k) H_(n,j) _(k) )^((r)) represents amatrix formed by selecting r columns from a rotated Hadamard matrixR_(i) _(k) H_(n,j) _(k) . The structure of the diagonal matrix R_(i)_(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance (for the uncorrelated channel); and for correlated channels,the columns should be selected in such a way that in a set {(R_(i) _(k)H_(n,j) _(k) )^((r))} formed by extracting one r-column sub-matrix fromeach matrix R_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximumgain in a zero direction of a spatial projection of an antenna array.Any other feasible method may also be employed for selection, and nolimitation is made thereon.

Specifically, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H) respectively, each of matrixes has a maximumchordal distance; and for correlated channels, the columns should beselected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H))^((r))} formed by extracting one r-column sub-matrix from eachmatrix R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H) respectively, each ofmatrixes has a maximum gain in a zero direction of a spatial projectionof an antenna array. Any other feasible method may also be employed forselection, and no limitation is made thereon.

502: Obtain a PM by using a second non-differential codebook and asecond diagonal differential codebook pre-stored locally and accordingto the reference PMI and the differential PMI.

The second non-differential codebook and the second diagonaldifferential codebook are consistent with the first non-differentialcodebook and the first diagonal differential codebook respectively.

Further, for an SU-MIMO system, the step of obtaining the PM by usingthe second non-differential codebook and the second diagonaldifferential codebook pre-stored locally and according to the referencePMI and the differential PMI may include:

obtaining a codeword corresponding to the reference PMI through queryfrom the second non-differential codebook according to the referencePMI, and obtaining a codeword corresponding to the differential PMIthrough query from the second diagonal differential codebook accordingto the differential PMI; and

multiplying the codeword corresponding to the reference PMI by thecodeword corresponding to the differential PMI to obtain amultiplication result for use as the PM.

Further, for an MU-MIMO system, the step of obtaining the PM by usingthe second non-differential codebook and the second diagonaldifferential codebook pre-stored locally and according to the referencePMI and the differential PMI may include:

calculating the PM by using the ZF-BF algorithm or based on the maximumSLNR criterion and according to reference PMIs and differential PMIs ofindividual data receiving ends that are simultaneously paired.

In the method for acquiring a PM according to the embodiment of thepresent invention, a PM is acquired by using a second non-differentialcodebook and a second diagonal differential codebook pre-stored locallyand according to a reference PMI and a differential PMI. The fact that acodeword included in the second diagonal differential codebook is adiagonal matrix can maintain amplitude characteristics (for example, aconstant modulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook or facilitate power distribution among antennas. Moreover, anon-differential codebook obtained from a rotated Hadamard matrix may beused as the second non-differential codebook. Individual columns of theHadamard matrix may be matched with eigenvectors of strongly correlatedchannels and weakly correlated channels in a uniform linear arraytransmitting antenna arrangement and a dual-polarized transmittingantenna arrangement respectively so as to improve the accuracy ofquantization. The rotated matrix is in the form of a diagonal matrix,and this can maintain a fine quantization of the space on basis of thequantization of the Hadamard matrix. Furthermore, each of elements ofthe Hadamard matrix is +1 or −1, which can maintain the constant moduluscharacteristic of the non-differential codebook; and multiplication ofthe Hadamard matrix with other matrixes or vectors may be simplifiedinto addition or subtraction operations, which can significantly reducethe computational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation. The individual columns of the normalizedHadamard matrix are orthogonal to each other, and this can maintain theunitary matrix characteristic of codewords in the non-differentialcodebook so that individual sent spatial streams are guaranteed to havethe same power distribution and, in case of a full rank, individualtransmitting antennas have the same power distribution. Additionally,the approach to obtain a non-differential codebook from a rotatedHadamard matrix may be applied to cases where the number of transmittingantennas is 2, 4, 8, 16, 32, 64 or the like, and the obtainednon-differential codebook may satisfy the constant moduluscharacteristic and the unitary matrix characteristic and reduce thecomputational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation.

Embodiment 8

Referring to FIG. 6, this embodiment of the present invention providesan apparatus for acquiring a PMI, where the apparatus includes:

a PMI acquiring module 601, configured to acquire a reference PMI and adifferential PMI according to a first non-differential codebook and afirst diagonal differential codebook, where a codeword included in thefirst diagonal differential codebook is a diagonal matrix.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention.Codewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order normalized Hadamard matrixcorresponding to j_(k), a value of n is equal to the number oftransmitting antennas, and (R_(i) _(k) H_(n,j) _(k) )^((r)) represents amatrix formed by selecting r columns from a rotated Hadamard matrixR_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance (for the uncorrelated channels); and for correlated channels,the columns should be selected in such a way that in a set {(R_(i) _(k)H_(n,j) _(k) )^((r))} formed by extracting one r-column sub-matrix fromeach matrix R_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximumgain in a zero direction of a spatial projection of an antenna array.Any other feasible method may also be employed for selection, and nolimitation is made thereon. Specifically, the codeword W_(k) ^((r))included in the first non-differential codebook may have the followingstructure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R, may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, δ_(i) _(k) _(,t) represents aphase shift, t=1, 2, . . . , n, and a value of n is equal to the numberof transmitting antennas. In the step of forming the matrix (R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H), which rcolumns are selected may be determined by using a correlation methoddepending on actual applications. For example, for uncorrelatedchannels, the columns should be selected in such a way that in a set{(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed by extractingone r-column sub-matrix from each matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), each of matrixes has a maximum chordal distance; and forcorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in a zerodirection of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

Further, the PMI acquiring module 601 may include:

a reference PMI calculating unit, configured to calculate the referencePMI based on a preset criterion and according to the firstnon-differential codebook; and

a differential PMI calculating unit, configured to, after the referencePMI is obtained by the reference PMI calculating unit, calculate thedifferential PMI based on the preset criterion and according to thefirst non-differential codebook, the first diagonal differentialcodebook, and the reference PMI; or

the PMI acquiring module 601 may include:

a reference PMI and differential PMI calculating unit, configured tocalculate the reference PMI and the differential PMI based on the presetcriterion and according to the first non-differential codebook and thefirst diagonal differential codebook.

Further, referring to FIG. 6, the apparatus further includes:

a PMI feedback module 602, configured to, after the reference PMI andthe differential PMI are obtained by the PMI acquiring module 601, feedback the reference PMI and the differential PMI to a data sending end sothat, according to the reference PMI and the differential PMI, a PM isobtained by the data sending end using a second non-differentialcodebook and a second diagonal differential codebook pre-stored locally,where the second non-differential codebook and the second diagonaldifferential codebook are consistent with the first non-differentialcodebook and the first diagonal differential codebook respectively.

In the apparatus for acquiring a PMI according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to improve the feedback performance; and the fact that acodeword included in the diagonal differential codebook is a diagonalmatrix can maintain amplitude characteristics (for example, a constantmodulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can maintain the constant moduluscharacteristic of the non-differential codebook. Moreover,multiplication of the Hadamard matrix with other matrixes or vectors maybe simplified into addition or subtraction operations, which cansignificantly reduce the computational complexity of CQI calculationbased on the SINR, PMI selection and rank adaptation. The individualcolumns of the normalized Hadamard matrix are orthogonal to each other,and this can maintain the unitary matrix characteristic of codewords inthe non-differential codebook so that individual sent spatial streamsare guaranteed to have the same power distribution and, in case of afull rank, individual transmitting antennas have the same powerdistribution. Additionally, the approach to obtain a non-differentialcodebook from a rotated Hadamard matrix may be applied to cases wherethe number of transmitting antennas is 2, 4, 8, 16, 32, 64 or the like,and the obtained non-differential codebook may satisfy the constantmodulus characteristic and the unitary matrix characteristic and reducethe computational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation.

Embodiment 9

Referring to FIG. 7, this embodiment of the present invention providesan apparatus for acquiring a PM, which includes a PMI receiving module701 and a PM acquiring module 702.

The PMI receiving module 701 is configured to receive a reference PMIand a differential PMI, where the reference PMI and the differential PMIare obtained according to a first non-differential codebook and a firstdiagonal differential codebook and then sent by a data receiving end,and a codeword included in the first diagonal differential codebook is adiagonal matrix.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention.Codewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) )^((r)) represents a matrix formed by selectingr columns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance (for the uncorrelated channels); and for correlated channels,the columns should be selected in such a way that in a set {(R_(i) _(k)H_(n,j) _(k) )^((r))} formed by extracting one r-column sub-matrix fromeach matrix R_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximumgain in a zero direction of a spatial projection of an antenna array.Any other feasible method may also be employed for selection, and nolimitation is made thereon. Specifically, the codeword W_(k) ^((r))included in the first non-differential codebook may have the followingstructure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2)),  …  , b_(i, t)𝕖^(jδ_(i_(k), t)),  …  , b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum chordal distance;and for correlated channels, the columns should be selected in such away that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))}formed by extracting one r-column sub-matrix from each matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in azero direction of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

The PM acquiring module 702 is configured to, after the reference PMIand the differential PMI are received by the PMI receiving module 701,obtain a PM by using a second non-differential codebook and a seconddiagonal differential codebook pre-stored locally and according to thereference PMI and the differential PMI, where the secondnon-differential codebook and the second diagonal differential codebookare consistent with the first non-differential codebook and the firstdiagonal differential codebook respectively.

Further, for an SU-MIMO system, the PM acquiring module 702 may include:

a codeword acquiring unit, configured to, after the reference PMI andthe differential PMI are received by the PMI receiving module 701,obtain a codeword corresponding to the reference PMI through query fromthe second non-differential codebook according to the reference PMI, andobtain a codeword corresponding to the differential PMI through queryfrom the second diagonal differential codebook according to thedifferential PMI; and

a first PM acquiring unit, configured to, after the codewordcorresponding to the differential PMI and the codeword corresponding tothe reference PMI are obtained by the codeword acquiring unit, multiplythe codeword corresponding to the reference PMI by the codewordcorresponding to the differential PMI to obtain a multiplication resultfor use as the PM.

Further, for an MU-MIMO system, the PM acquiring module 702 includes:

a second PM acquiring unit, configured to, after the reference PMI andthe differential PMI are received by the PMI receiving module 701,calculate the PM by using the ZF-BF algorithm or based on the maximumSLNR criterion and according to reference PMIs and differential PMIs ofindividual data receiving ends that are simultaneously paired.

In the apparatus for acquiring a PM according to the embodiment of thepresent invention, acquiring a reference PMI and a differential PMIaccording to a non-differential codebook and a diagonal differentialcodebook can reduce the feedback overhead and improve the feedbackprecision so as to further improve the feedback performance; and thefact that a codeword included in the diagonal differential codebook is adiagonal matrix can maintain amplitude characteristics (for example, aconstant modulus characteristic, and a finite character set constraintcharacteristic) of elements already existing in the non-differentialcodebook. Moreover, a non-differential codebook obtained from a rotatedHadamard matrix may be used. Individual columns of the Hadamard matrixmay be matched with eigenvectors of strongly correlated channels andweakly correlated channels in a uniform linear array transmittingantenna arrangement and a dual-polarized transmitting antennaarrangement respectively so as to improve the accuracy of quantization.The rotated matrix is in the form of a diagonal matrix, and this canmaintain a fine quantization of the space on basis of the quantizationof the Hadamard matrix. Furthermore, each of elements of the Hadamardmatrix is +1 or −1, which can maintain the constant moduluscharacteristic of the non-differential codebook. Furthermore,multiplication of the Hadamard matrix with other matrixes or vectors maybe simplified into addition or subtraction operations, which cansignificantly reduce the computational complexity of CQI calculationbased on the SINR, PMI selection and rank adaptation. The individualcolumns of the normalized Hadamard matrix are orthogonal to each other,and this can maintain the unitary matrix characteristic of codewords inthe non-differential codebook so that individual sent spatial streamsare guaranteed to have the same power distribution and, in case of afull rank, individual transmitting antennas have the same powerdistribution. Further, the approach to obtain a non-differentialcodebook from a rotated Hadamard matrix may be applied to cases wherethe number of transmitting antennas is 2, 4, 8, 16, 32, 64 or the like,and the obtained non-differential codebook may satisfy the constantmodulus characteristic and the unitary matrix characteristic and reducethe computational complexity of CQI calculation based on the SINR, PMIselection and rank adaptation.

Embodiment 10

Referring to FIG. 8, this embodiment of the present invention provides amethod for acquiring a PMI, where the method includes the followingsteps.

801: Calculate a non-differential PMI based on a preset criterion andaccording to a first non-differential codebook.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention.Codewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) )^((r)) represents a matrix formed by selectingr columns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2)) ,  …  , b_(i, t)𝕖^(jδ_(i_(k), t)), …  , b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of an antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon.

Specifically, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2)),  …  , b_(i, t)𝕖^(jδ_(i_(k), t)),  …  , b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum chordal distance;and for correlated channels, the columns should be selected in such away that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))}formed by extracting one r-column sub-matrix from each matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in azero direction of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

Optionally, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may further have the following structure:W _(k) ^((r)) =R _(i) _(k) B _(n,j) _(k) ^((r))

where, k represents a PMI included in the non-differential codebookW^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents the number ofcodewords included in the non-differential codebook W^((r)), rrepresents a rank of the codewords included in the non-differentialcodebook W^((r)), i_(k) represents an index of a diagonal matrix R_(i)_(k) corresponding to k, R_(i) _(k) represents a n^(th) order diagonalmatrix corresponding to i_(k), B_(n,j) _(k) ^((r)) represents a codewordin a non-differential codebook having a rank of r for n transmittingantennas and corresponding to an index j_(k), and j_(k) corresponds tok.

Further, referring to FIG. 8, after acquiring the first PMI, the methodmay further include:

802: Feed back the non-differential PMI to a data sending end.

803: The data sending end receives the non-differential PMI and,according to the non-differential PMI, obtains a PM by using a secondnon-differential codebook pre-stored locally.

The second non-differential codebook is consistent with the firstnon-differential codebook.

In the method for acquiring a PMI according to the embodiment of thepresent invention, a non-differential codebook obtained from a rotatedHadamard matrix is used. Individual columns of the Hadamard matrix maybe matched with eigenvectors of strongly correlated channels and weaklycorrelated channels in a uniform linear array transmitting antennaarrangement and a dual-polarized transmitting antenna arrangementrespectively so as to improve the accuracy of quantization. The rotatedmatrix is in the form of a diagonal matrix, and this can maintain a finequantization of the space on basis of the quantization of the Hadamardmatrix. Furthermore, each of elements of the Hadamard matrix is +1 or−1, which can maintain the constant modulus characteristic of thenon-differential codebook. Additionally, multiplication of the Hadamardmatrix with other matrixes or vectors may be simplified into addition orsubtraction operations, which can significantly reduce the computationalcomplexity of CQI calculation based on the SINR, PMI selection and rankadaptation. The individual columns of the normalized Hadamard matrix areorthogonal to each other, and this can maintain the unitary matrixcharacteristic of codewords in the non-differential codebook so thatindividual sent spatial streams are guaranteed to have the same powerdistribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Further, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.

Embodiment 11

Referring to FIG. 9, this embodiment of the present invention providesan apparatus for acquiring a PMI, where the apparatus includes:

a non-differential PMI acquiring module 901, configured to calculate anon-differential PMI based on a preset criterion and according to afirst non-differential codebook, where codewords included in the firstnon-differential codebook are obtained from a rotated Hadamard matrix.

The preset criterion is similar to that in Embodiment 2, and will not befurther described herein. The first non-differential codebook W^((r))may be a non-differential codebook set according to the embodiment ofthe present invention. The codewords in the first non-differentialcodebook W^((r)) are obtained from a rotated Hadamard matrix, andspecifically, a codeword W_(k) ^((r)) included in the firstnon-differential codebook W^((r)) may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), k_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order normalized Hadamard matrixcorresponding to j_(k), a value of n is equal to the number oftransmitting antennas, and (R_(i) _(k) H_(n,j) _(k) )^((r)) represents amatrix formed by selecting r columns from a rotated Hadamard matrixR_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of an antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon.

Specifically, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(δ_(i_(k), t))  …  b_(i, n)𝕖^(δ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum chordal distance;and for correlated channels, the columns should be selected in such away that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))}formed by extracting one r-column sub-matrix from each matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in azero direction of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

Further, referring to FIG. 9, the apparatus may further include:

a non-differential PMI feedback module 902, configured to, after thenon-differential PMI is obtained by the non-differential PMI acquiringmodule 901, feed back the non-differential PMI to a data sending end sothat, according to the non-differential PMI, a PM is obtained by thedata sending end using a second non-differential codebook pre-storedlocally, where the second non-differential codebook is consistent withthe first non-differential codebook.

In the apparatus for acquiring a PMI according to the embodiment of thepresent invention, a non-differential codebook obtained from a rotatedHadamard matrix is used. Individual columns of the Hadamard matrix maybe matched with eigenvectors of strongly correlated channels and weaklycorrelated channels in a uniform linear array transmitting antennaarrangement and a dual-polarized transmitting antenna arrangementrespectively so as to improve the accuracy of quantization. The rotatedmatrix is in the form of a diagonal matrix, and this can maintain a finequantization of the space on basis of the quantization of the Hadamardmatrix. Furthermore, each of elements of the Hadamard matrix is +1 or−1, which can maintain the constant modulus characteristic of thenon-differential codebook. Additionally, multiplication of the Hadamardmatrix with other matrixes or vectors may be simplified into addition orsubtraction operations, which can significantly reduce the computationalcomplexity of CQI calculation based on the SINR, PMI selection and rankadaptation. The individual columns of the normalized Hadamard matrix areorthogonal to each other, and this can maintain the unitary matrixcharacteristic of codewords in the non-differential codebook so thatindividual sent spatial streams are guaranteed to have the same powerdistribution and, in case of a full rank, individual transmittingantennas have the same power distribution. Further, the approach toobtain a non-differential codebook from a rotated Hadamard matrix may beapplied to cases where the number of transmitting antennas is 2, 4, 8,16, 32, 64 or the like, and the obtained non-differential codebook maysatisfy the constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.

Embodiment 12

Referring to FIG. 10, this embodiment of the present invention providesa method for acquiring a PM, where the method includes the followingsteps.

1001: Receive a non-differential PMI, where the non-differential PMI isobtained according to a first non-differential codebook and then sent bya data receiving end, and codewords included in the firstnon-differential codebook are obtained from a rotated Hadamard matrix.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention. Thecodewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) )^((r)) represents a matrix formed by selectingr columns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of an antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon.

Specifically, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2)), …  , b_(i, t)𝕖^(jδ_(i_(k), t)), …  , b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum chordal distance;and for correlated channels, the columns should be selected in such away that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))}formed by extracting one r-column sub-matrix from each matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in azero direction of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

1002: Obtain a PM by using a second non-differential codebook pre-storedlocally and according to the non-differential PMI, where the secondnon-differential codebook is consistent with the first non-differentialcodebook.

Further, for an SU-MIMO system, the step of obtaining the PM by usingthe second non-differential codebook pre-stored locally and according tothe non-differential PMI includes: obtaining a codeword corresponding tothe non-differential PMI through query from the second non-differentialcodebook according to the non-differential PMI; and using the codewordcorresponding to the non-differential PMI as the PM.

Further, for an MU-MIMO system, the step of obtaining the PM by usingthe second non-differential codebook pre-stored locally and according tothe non-differential PMI includes: calculating the PM by using the ZF-BFalgorithm or based on the maximum SLNR criterion and according tonon-differential PMIs of individual data receiving ends that aresimultaneously paired.

In the method for acquiring a PM according to the embodiment of thepresent invention, a PM is acquired according to a non-differential PMIand a non-differential codebook is obtained from a rotated Hadamardmatrix. Individual columns of the Hadamard matrix may be matched witheigenvectors of strongly correlated channels and weakly correlatedchannels in a uniform linear array transmitting antenna arrangement anda dual-polarized transmitting antenna arrangement respectively so as toimprove the accuracy of quantization. The rotated matrix is in the formof a diagonal matrix, and this can maintain a fine quantization of thespace on basis of the quantization of the Hadamard matrix. Furthermore,each of elements of the Hadamard matrix is +1 or −1, which can maintainthe constant modulus characteristic of the non-differential codebook.Additionally, multiplication of the Hadamard matrix with other matrixesor vectors may be simplified into addition or subtraction operations,which can significantly reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation. Theindividual columns of the normalized Hadamard matrix are orthogonal toeach other, and this can maintain the unitary matrix characteristic ofcodewords in the non-differential codebook so that individual sentspatial streams are guaranteed to have the same power distribution and,in case of a full rank, individual transmitting antennas have the samepower distribution. Additionally, the approach to obtain anon-differential codebook from a rotated Hadamard matrix may be appliedto cases where the number of transmitting antennas is 2, 4, 8, 16, 32,64 or the like, and the obtained non-differential codebook may satisfythe constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.

Embodiment 13

Referring to FIG. 11, this embodiment of the present invention providesan apparatus for acquiring a PM, which includes a non-differential PMIreceiving module 1101 and a non-differential PM acquiring module 1102.

The non-differential PMI receiving module 1101 is configured to receivea non-differential PMI, where the non-differential PMI is obtainedaccording to a first non-differential codebook and then sent by a datareceiving end, and codewords included in the first non-differentialcodebook are obtained from a rotated Hadamard matrix.

The first non-differential codebook W^((r)) may be a non-differentialcodebook set according to the embodiment of the present invention. Thecodewords in the first non-differential codebook W^((r)) are obtainedfrom a rotated Hadamard matrix, and specifically, a codeword W_(k)^((r)) included in the first non-differential codebook W^((r)) may havethe following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}} )^{(r)}}$

where, k represents a non-differential PMI included in the firstnon-differential codebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))|represents the number of codewords included in the firstnon-differential codebook W^((r)), r represents a rank of the codewordsincluded in the first non-differential codebook, i_(k) represents anindex of a diagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k)represents a n^(th) order diagonal matrix corresponding to i_(k), j_(k)represents an index of a normalized Hadamard matrix corresponding to k,H_(n,j) _(k) represents a n^(th) order Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) )^((r)) represents a matrix formed by selectingr columns from a rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) .

The structure of the diagonal matrix R₄ may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2))  …  b_(i, t)𝕖^(jδ_(i_(k), t))  …  b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) )^((r)) by selecting r columns from therotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) , which r columns areselected may be determined by using a correlation method depending onactual applications. For example, for uncorrelated channels, the columnsshould be selected in such a way that in a set {(R_(i) _(k) H_(n,j) _(k))^((r))} formed by extracting one r-column sub-matrix from each matrixR_(i) _(k) H_(n,j) _(k) , each of matrixes has a maximum chordaldistance; and for correlated channels, the columns should be selected insuch a way that in a set {(R_(i) _(k) H_(n,j) _(k) )^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) , each of matrixes has a maximum gain in a zero direction of aspatial projection of an antenna array. Any other feasible method mayalso be employed for selection, and no limitation is made thereon.

Specifically, the codeword W_(k) ^((r)) included in the firstnon-differential codebook may have the following structure:

$W_{k}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{k}}H_{n,j_{k}}R_{i_{k}}^{H}} )^{(r)}}$

where, k represents a PMI included in the first non-differentialcodebook W^((r)), k=0, 1 . . . |W^((r))|−1, |W^((r))| represents thenumber of codewords included in the first non-differential codebookW^((r)), r represents a rank of the codewords included in the firstnon-differential codebook W^((r)), i_(k) represents an index of adiagonal matrix R_(i) _(k) corresponding to k, R_(i) _(k) represents an^(th) order diagonal matrix corresponding to i_(k), j_(k) represents anindex of a normalized Hadamard matrix corresponding to k, H_(n,j) _(k)represents a n^(th) order normalized Hadamard matrix corresponding toj_(k), a value of n is equal to the number of transmitting antennas, and(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H).

The structure of the diagonal matrix R_(i) _(k) may be represented as:

R_(i_(k)) = diag{b_(i_(k), 1)𝕖^(jδ_(i_(k), 1)), b_(i, 2)𝕖^(jδ_(i_(k), 2)), …  , b_(i, t)𝕖^(jδ_(i_(k), t)), …  , b_(i, n)𝕖^(jδ_(i_(k), n))}

where, b_(i) _(k) _(,t) is a real number, j²=−1, δ_(i) _(k) _(,t)represents a phase shift, t=1, 2, . . . , n, and a value of n is equalto the number of transmitting antennas. In the step of forming thematrix (R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r)) by selecting rcolumns from the rotated Hadamard matrix R_(i) _(k) H_(n,j) _(k) R_(i)_(k) ^(H), which r columns are selected may be determined by using acorrelation method depending on actual applications. For example, foruncorrelated channels, the columns should be selected in such a way thatin a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))} formed byextracting one r-column sub-matrix from each matrix R_(i) _(k) H_(n,j)_(k) R_(i) _(k) ^(H), each of matrixes has a maximum chordal distance;and for correlated channels, the columns should be selected in such away that in a set {(R_(i) _(k) H_(n,j) _(k) R_(i) _(k) ^(H))^((r))}formed by extracting one r-column sub-matrix from each matrix R_(i) _(k)H_(n,j) _(k) R_(i) _(k) ^(H), each of matrixes has a maximum gain in azero direction of a spatial projection of an antenna array. Any otherfeasible method may also be employed for selection, and no limitation ismade thereon.

The non-differential PM acquiring module 1102 is configured to, afterthe non-differential PMI is received by the non-differential PMIreceiving module 1101, calculate a PM by using a second non-differentialcodebook pre-stored locally and according to the non-differential PMI,where the second non-differential codebook is consistent with the firstnon-differential codebook.

Further, for an SU-MIMO system, the non-differential PM acquiring module1102 is configured to, after the non-differential PMI is received by thenon-differential PMI receiving module 1101, obtain a codewordcorresponding to the non-differential PMI through query from the secondnon-differential codebook according to the non-differential PMI and usethe codeword corresponding to the non-differential PMI as the PM.

Further, for an MU-MIMO system, the PM acquiring module 1102 isconfigured to, after the non-differential PMI is received by thenon-differential PMI receiving module 1101, calculate the PM based on byusing the ZF-BF algorithm or based on the maximum SLNR criterion andaccording to non-differential PMIs of individual data receiving endsthat are simultaneously paired.

In the apparatus for acquiring a PM according to the embodiment of thepresent invention, a PM is acquired according to a non-differential PMIand a non-differential codebook is obtained from a rotated Hadamardmatrix. Individual columns of the Hadamard matrix may be matched witheigenvectors of strongly correlated channels and weakly correlatedchannels in a uniform linear array transmitting antenna arrangement anda dual-polarized transmitting antenna arrangement respectively so as toimprove the accuracy of quantization. The rotated matrix is in the formof a diagonal matrix, and this can maintain a fine quantization of thespace on basis of the quantization of the Hadamard matrix. Furthermore,each of elements of the Hadamard matrix is +1 or −1, which can maintainthe constant modulus characteristic of the non-differential codebook.Additionally, multiplication of the Hadamard matrix with other matrixesor vectors may be simplified into addition or subtraction operations,which can significantly reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation. Theindividual columns of the normalized Hadamard matrix are orthogonal toeach other, and this can maintain the unitary matrix characteristic ofcodewords in the non-differential codebook so that individual sentspatial streams are guaranteed to have the same power distribution and,in case of a full rank, individual transmitting antennas have the samepower distribution. Additionally, the approach to obtain anon-differential codebook from a rotated Hadamard matrix may be appliedto cases where the number of transmitting antennas is 2, 4, 8, 16, 32,64 or the like, and the obtained non-differential codebook may satisfythe constant modulus characteristic and the unitary matrixcharacteristic and reduce the computational complexity of CQIcalculation based on the SINR, PMI selection and rank adaptation.

All or part of the technical solutions provided in the above embodimentscan be achieved through software programming, and the software programsare stored in a readable storage medium such as a hard disk, a compactdisk (CD) or a soft disk in a computer.

What described above is only preferred embodiments of the presentinvention and is not intended to limit the present invention. Anymodification, equivalent replacement and improvement made within thespirits and principles of the present invention are all covered withinthe scope of the present invention.

What is claimed is:
 1. A method for acquiring a Precoding MatrixIndicator (PMI), comprising: obtaining a first PMI and a second PMI,wherein the combination of the first PMI and the second PMI indicates aprecoding matrix {circumflex over (V)} used for generating data to besent by a data sending end; and sending the first PMI and the second PMIto the data sending end; wherein the precoding matrix {circumflex over(V)} satisfies {circumflex over (V)}=C_(k) W_(n), n is the first PMI,W_(n) is a codeword corresponding to the first PMI, k is the second PMI,C_(k) is a codeword corresponding to the second PMI, and the codewordC_(k) is a diagonal matrix.
 2. The method for acquiring a PMI accordingto claim 1, wherein the codeword C_(k) has the following structure:C _(k)=diag{e ^(jθ) ^(k,1) ,e ^(jθ) ^(k,2) , . . . ,e ^(jθ) ^(k,i) , . .. ,e ^(jθ) ^(k,N) }, j²=−1, N represents the number of transmittingantennas and is a positive integer, θ_(k,i) represents a phase shift,and i=1, 2 . . . N.
 3. The method for acquiring a PMI according to claim1, wherein the codeword C_(k) has the following structure:C _(k)=diag{S _(m) ,e ^(jφ) ^(q) S _(m)}, wherein S_(m)=diag{e^(jθ)^(m,1) , e^(jθ) ^(m,2) , . . . , e^(jθ) ^(m,i) , . . . , e^(jθ) ^(m,N/2)}, j²=−1, N represents the number of transmitting antennas and is aneven integer, φ_(q) and θ_(m,i) represent phase shifts, m and q arenatural numbers, and i=1, 2 . . . , N/2.
 4. The method for acquiring aPMI according to claim 1, wherein the codeword W_(n) has the followingstructure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{n}}H_{N,j_{n}}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) )^((r)) represents a matrix formed byselecting r columns from a rotated Hadamard matrix (R_(i) _(n) H_(N,j)_(n) )^((r)); or the codeword W_(n) has the following structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{n}}H_{N,j_{n}}R_{i_{n}}^{H}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) R_(i) _(n) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(n)H_(N,j) _(n) R_(i) _(n) ^(H); or the codeword W_(n) has the followingstructure:W _(n) ^((r)) =R _(i) _(n) B _(N,i) _(n) ^((r)), wherein r represents arank, i_(n) represents an index of a diagonal matrix R_(i) _(n)corresponding to n, R_(i) _(n) represents a N^(th) order diagonal matrixcorresponding to i_(n), B_(n,j) _(k) ^((r)) represents a codeword havinga rank of r for n transmitting antennas and corresponding to an indexj_(n), and j_(n) corresponds to n.
 5. The method for acquiring a PMIaccording to claim 1, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI.
 6. The method for acquiring a PMIaccording to claim 1, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI which is fed back for selected Msub-band(s).
 7. The method for acquiring a PMI according to claim 1,wherein the first PMI is a broadband PMI, and the second PMI is a PMIwhich is fed back for a bandwidth part.
 8. A method for acquiring aPrecoding Matrix Indicator (PMI), comprising: receiving, by a datasending end, a first PMI and a second PMI, wherein the combination ofthe first PMI and the second PMI indicates a precoding matrix{circumflex over (V)} used for generating data to be sent by the datasending end; and obtaining, by the data sending end, the precodingmatrix {circumflex over (V)} according to the first PMI and the secondPMI; wherein the precoding matrix {circumflex over (V)} satisfies{circumflex over (V)}=C_(k) W_(n), n is the first PMI, W_(n) is acodeword corresponding to the first PMI, k is the second PMI, C_(k) is acodeword corresponding to the second PMI, and the codeword C_(k) is adiagonal matrix.
 9. The method for acquiring a PMI according to claim 8,wherein the codeword C_(k) has the following structure:C _(k)=diag{e ^(jθ) _(k,1) ,e ^(jθ) _(k,2) , . . . ,e ^(jθ) _(k,i) , . .. ,e ^(jθ) _(k,N) }, j²=−1, N represents the number of transmittingantennas and is a positive integer, θ_(k,i) represents a phase shift,and i=1, 2 . . . N.
 10. The method for acquiring a PMI according toclaim 8, wherein the codeword C_(k) has the following structure:C _(k)=diag{S _(m) ,e ^(jφ) _(q) S _(m)}, wherein S_(m)=diag{e^(jθ)_(m,1) , e^(jθ) _(m,2), . . . , e^(jθ) _(m,i), . . . , e^(jθ) _(m,N/2)}, j²=−1, N represents the number of transmitting antennas and is aneven integer, φ_(q) and θ_(m,i) represent phase shifts, m and q arenatural numbers, and i=1, 2 . . . , N/2.
 11. The method for acquiring aPMI according to claim 8, wherein the codeword W_(n) has the followingstructure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{n}}H_{N,j_{n}}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) )^((r)) represents a matrix formed byselecting r columns from a rotated Hadamard matrix (R_(i) _(n) H_(N,j)_(n) )^((r)); or the codeword W_(n) has the following structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}}( {R_{i_{n}}H_{N,j_{n}}R_{i_{n}}^{H}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) R_(i) _(n) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(n)H_(N,j) _(n) R_(i) _(n) ^(H); or the codeword W_(n) has the followingstructure:W _(n) ^((r)) =R _(i) _(n) B _(N,j) _(n) ^((r)), wherein r represents arank, i_(n) represents an index of a diagonal matrix R_(i) _(n)corresponding to n, R_(i) _(n) represents a N^(th) order diagonal matrixcorresponding to i_(n), B_(n,j) _(k) ^((r)) represents a codeword havinga rank of r for n transmitting antennas and corresponding to an indexj_(n), and j_(n) corresponds to n.
 12. The method for acquiring a PMIaccording to claim 8, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI.
 13. The method for acquiring a PMIaccording to claim 8, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI which is fed back for selected Msub-band(s).
 14. The method for acquiring a PMI according to claim 8,wherein the first PMI is a broadband PMI, and the second PMI is a PMIwhich is fed back for a bandwidth part.
 15. An apparatus for acquiring aPrecoding Matrix Indicator (PMI), comprising: a processor, configured toobtain a first PMI and a second PMI, wherein the combination of thefirst PMI and the second PMI indicates a precoding matrix {circumflexover (V)} used for generating data to be sent by a data sending end; anda transmitter, configured to send the first PMI and the second PMI tothe data sending end; wherein the precoding matrix {circumflex over (V)}satisfies {circumflex over (V)}=C_(k) W_(n), n is the first PMI, W_(n)is a codeword corresponding to the first PMI, k is the second PMI, C_(k)is a codeword corresponding to the second PMI, and the codeword C_(k) isa diagonal matrix.
 16. The apparatus for acquiring a PMI according toclaim 15, wherein the codeword C_(k) has the following structure:C _(k)=diag{e ^(jθ) ^(k,1) ,e ^(jθ) ^(k,2) , . . . ,e ^(jθ) ^(k,i) , . .. ,e ^(jθ) ^(k,N) }, j²=−1, N represents the number of transmittingantennas and is a positive integer, θ_(k,i) represents a phase shift,and i=1, 2 . . . N.
 17. The apparatus for acquiring a PMI according toclaim 15, wherein the codeword C_(k) has the following structure:C _(k)=diag{S _(m) ,e ^(jφ) ^(q) S _(m)}, wherein S_(m)=diag{e^(jθ)^(m,1) , e^(jθ) ^(m,3) , . . . , e^(jθ) ^(m,i) , . . . , e^(jθ) ^(m,N/2)}, j²=−1, N represents the number of transmitting antennas and is aneven integer, φ_(q) and θ_(m,i) represent phase shifts, m and q arenatural numbers, and i=1, 2 . . . , N/2.
 18. The apparatus for acquiringa PMI according to claim 15, wherein the codeword W_(n) has thefollowing structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{n}}H_{N,j_{n}}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponds to n, R_(i) _(n) represents a N^(th) orderdiagonal matrix corresponding to i_(n), j_(n) represents an index of anormalized Hadamard matrix corresponding to n, H_(N,j) _(n) represents aN^(th) order normalized Hadamard matrix corresponding to j_(n), a valueof N is equal to the number of the transmitting antennas, and (R_(i)_(n) H_(N,j) _(n) )^((r)) represents a matrix formed by selecting rcolumns from a rotated Hadamard matrix (R_(i) _(n) H_(N,j) _(n) )^((r));or the codeword W_(n) has the following structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{n}}H_{N,j_{n}}R_{i_{n}}^{H}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) R_(i) _(n) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(n)H_(N,j) _(n) R_(i) _(n) ^(H); or the codeword W_(n) has the followingstructure:W _(n) ^((r)) =R _(i) _(n) B _(N,j) _(n) ^((r)), wherein r represents arank, i_(n) represents an index of a diagonal matrix R_(i) _(n)corresponding to n, R_(i) _(n) represents a N^(th) order diagonal matrixcorresponding to i_(n), B_(n,j) _(k) ^((r)) represents a codeword havinga rank of r for n transmitting antennas and corresponding to an indexj_(n), and j_(n) corresponds to n.
 19. The apparatus for acquiring a PMIaccording to claim 15, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI.
 20. The apparatus for acquiring a PMIaccording to claim 15, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI which is fed back for selected Msub-band(s).
 21. The apparatus for acquiring a PMI according to claim15, wherein the first PMI is a broadband PMI, and the second PMI is aPMI which is fed back for a bandwidth part.
 22. An apparatus foracquiring a Precoding Matrix Indicator (PMI), comprising: a receiver,configured to receive a first PMI and a second PMI, wherein thecombination of the first PMI and the second PMI indicates a precodingmatrix {circumflex over (V)} used for generating data to be sent by theapparatus; and a processor, configured to obtain the precoding matrix{circumflex over (V)} according to the first PMI and the second PMI;wherein the precoding matrix {circumflex over (V)} satisfies {circumflexover (V)}=C_(k) W_(n), n is the first PMI, W_(n) is a codewordcorresponding to the first PMI, k is the second PMI, C_(k) is a codewordcorresponding to the second PMI, and the codeword C_(k) is a diagonalmatrix.
 23. The apparatus for acquiring a PMI according to claim 22,wherein the codeword C_(k) has the following structure:C _(k)==diag{e ^(jθ) ^(k,1) ,e ^(jθ) ^(k,2) , . . . ,e ^(jθ) ^(k,i) , .. . ,e ^(jθ) ^(k,N) }, j²=−1, N represents the number of transmittingantennas and is a positive integer, θ_(k,i) represents a phase shift,and i=1, 2 . . . N.
 24. The apparatus for acquiring a PMI according toclaim 22, wherein the codeword C_(k) has the following structure:C _(k)=diag{S _(m) ,e ^(jφ) ^(q) S _(m)}, wherein S_(m)=diag{e^(jθ)^(m,1) , e^(jθ) ^(m,2) , . . . , e^(jθ) ^(m,i) , . . . , e^(jθ) ^(m,N/2)}, j²=−1, N represents the number of transmitting antennas and is aneven integer, φ_(q) and θ_(m,i) represent phase shifts, m and q arenatural numbers, and i=1, 2 . . . , N/2.
 25. The apparatus for acquiringa PMI according to claim 22, wherein the codeword W_(n) has thefollowing structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{n}}H_{N,j_{n}}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) )^((r)) represents a matrix formed byselecting r columns from a rotated Hadamard matrix (R_(i) _(n) H_(N,j)_(n) )^((r)); or the codeword W_(n) has the following structure:${W_{n}^{(r)} = {\frac{1}{\sqrt{r}\;}( {R_{i_{n}}H_{N,j_{n}}R_{i_{n}}^{H}} )^{(r)}}},$wherein r represents a rank, i_(n) represents an index of a diagonalmatrix R_(i) _(n) corresponding to n, R_(i) _(n) represents a N^(th)order diagonal matrix corresponding to i_(n), j_(n) represents an indexof a normalized Hadamard matrix corresponding to n, H_(N,j) _(n)represents a N^(th) order normalized Hadamard matrix corresponding toj_(n), a value of N is equal to the number of the transmitting antennas,and (R_(i) _(n) H_(N,j) _(n) R_(i) _(n) ^(H))^((r)) represents a matrixformed by selecting r columns from a rotated Hadamard matrix R_(i) _(n)H_(N,j) _(n) R_(i) _(n) ^(H); or the codeword W_(n) has the followingstructure:W _(n) ^((r)) =R _(i) _(n) B _(N,j) _(n) ^((r)), wherein r represents arank, i_(n) represents an index of a diagonal matrix R_(i) _(n)corresponding to n, R_(i) _(n) represents a N^(th) order diagonal matrixcorresponding to i_(n), B_(n,j) _(k) ^((r)) represents a codeword havinga rank of r for n transmitting antennas and corresponding to an indexj_(n), and j_(n) corresponds to n.
 26. The apparatus for acquiring a PMIaccording to claim 22, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI.
 27. The apparatus for acquiring a PMIaccording to claim 22, wherein the first PMI is a broadband PMI, and thesecond PMI is a sub-band PMI which is fed back for selected Msub-band(s).
 28. The apparatus for acquiring a PMI according to claim22, wherein the first PMI is a broadband PMI, and the second PMI is aPMI which is fed back for a bandwidth part.